1 CHAPTER 1- Page 1-116 - Shodhgangashodhganga.inflibnet.ac.in/bitstream/10603/7156/15/15_chapter 3.pdf · Biology of dominant spiders Ph. D. Thesis 139 Chapter 3 BIOLOGY OF DOMINANT

Chapter 3

BIOLOGY OF DOMINANT SPIDERS

IN KUTTANAD RICE AGROECOSYSTEM

CONTENTS

Page No.

3.1. Introduction 139

3.2. Review of Literature 139

Feeding behaviour 141

Sperm induction 143

Courtship behaviour 143

Mating behaviour 145

Cocoon spinning behaviour 145

Phenology 145

3.3. Materials and Methods 146

3.4. Results 147

Araneus ellipticus 147

Pardosa pseudoannulata 150

Tetragnatha mandibulata 153

3.5. Discussion 157

Feeding behaviour 157

Phenology 157

Reproductive behaviour 159

Sexual conflict 160

Cocoon spinning 160

Life history 161

Biology of dominant spiders

Ph. D. Thesis 139

Chapter 3

BIOLOGY OF DOMINANT SPIDERS

IN KUTTANAD RICE AGROECOSYSTEM

3. 1. Introduction Spiders occupy an important part of the overall predatory

arthropod fauna in different terrestrial ecosystems (Riechert & Lockley, 1984). They are also known to play an important role in the regulation of pest species in agriculture (Dean et al., 1982; Culin & Yeargan, 1983; Mansour et al., 1983; Oraze & Grigarick, 1989; Riechert & Bishop, 1990; Barrion & Litsinger, 1995). Baseline information on life history and biology is fundamental for ecological work and is also important in further investigation of the potential of spiders as biological control agents. However, life history studies have been done on limited species of spiders. One reason for this is the lack of reliable rearing methods to determine life histories and other biological data directly from laboratory cultures. Another reason is the lack of appropriate artificial diets. Since spiders are primarily carnivorous, they require behavioural cues from the prey to initiate attack and feeding (Riechert & Luczak, 1982). This makes the rearing and maintenance of spiders in the laboratory a very laborious task. Moreover, it appears that most spiders must feed on a variety of insect prey species to obtain the optimum nutrition for survival and reproduction (Uetz et al., 1999). The need to rear different insect prey species makes it especially difficult to culture spiders in the laboratory. Formulation of artificial diet would greatly facilitate laboratory rearing of spiders; however, this requires knowledge of the complete nutritional requirements of individual spiders.

3. 2. Review of Literature

In the past, spiders were considered as mysterious or dangerous animals and numerous beliefs were linked to them; this state of mind was particularly developed in the last century, even in the scientific circles. Therefore, acquisition of knowledge of the biology, ecology and taxonomy of spiders has been considerably delayed compared to other related groups like insects. Various ecological field studies carried out in the past decades have allowed the emergence of numerous new faunistical and biological data on spiders. As has been developed in this chapter, this specific information on spiders constitutes the basis for any

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field survey dealing with biological control or bioindicators. Kim (1998) pointed out that if spiders are being used as biological control agents, it is very important to understand their life styles.

The potential of spiders as natural control agents of destructive insect has created a considerable interest in understanding their life histories and especially their predacious habits in the attempt to evaluate their importance as enemies of phytophagous insects. Despite this interest, there have been relatively few studies that focused on the biology of specific spider taxa. The life history of a spider is influenced by many environmental factors such as the amount of food available, temperature, humidity and illumination (Miyashitha, 1968). Both Indian and foreign authors studied the biology and behavioural aspects of spiders. Levy (1970) reviewed the literature and published a list of species for which data on the number of instars and duration of development were available. Studies of Jambunathan (1905) revealed that Stegodyphus sarasinorum has an annual life history. Bradoo (1972) studied the cocoon spinning behaviour and fecundity of S. sarasinorum.The life cycle of Uloborus ferokus has been studied by Bradoo (1982) and that of Octonoba octonarius by Peaslee & Peck (1983). Bakken (1986) studied the life history of Araneus cucurbitus and Bunn (1982) that of A. diadematus. Edmunds (1982) studied the detailed biology of Argiope flavipalpis trifasciata. Robinson & Robinson (1976) published the biology of Nephila maculata. Pollard & Jackson (1984) studied the biology of Clubiona cambridgei. Likewise, Peck & Whitcomb (1968) studied the biology of Cheiracanthium inclusum. The life cycle of Rabidosa punctulata including its biology and ecology was studied by Eason & Whitcomb (1965). They also studied the biology of Pardosa lapidicina and Hickle (1981) studied the life history of Oxyopes salticus. Patel & Bradoo (1986) conducted a detailed study on the biology of Artema atlanta of the family Pholcidae. Vincent (1974) studied the biology of Tetragnatha extensa in the filed condition. Robinson & Robinson (1973) conducted a comparative study on the courtship and mating behaviour of tropical araneid spiders. Elgar (1991) studied the sexual cannibalism, size dimorphism and courtship behaviour in orb weaving spiders. Coddington et al. (1997) studied the sexual difference in body size of different species of spiders and they concluded that in all families females are bigger than their male counterparts. Prenter et al.(1999) studied the influence of sexual size dimorphism in reproductive investment in female spiders and its implications for the differential mortality. Prenter et al. (1997) studied the relation between size of mother and number of eggs and young in some spiders and its significance on the evolution of size. Salvestrini & Gasnier (2001) analyzed the difference in the activity of juveniles, females and males of two hunting spider species. The studies of Schmitt et al. (1990) on daily


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locomotor activity of three spider species revealed that males are more wanders than females. Schneider et al. (2000) studied the effect of sperm competition and small size advantage for the male of the golden orb web spider.

Bleckmann & Rovner (1984) studied the role of vegetation structure and wind velocity in site slection of spiders. Opell (1989) and Nunez (2001) studied the egg case of spiders of the family Uloboridae and Tetragnathidae and the effect of habitat disturbances on the cocoon construction. Jambunathan (1905), Norgaard (1941) and Bradoo (1982) studied the cocoon spinning behaviour, ecology and fecundity of Indian social spiders. Bradoo (1972) also studied egg parasitism and kleptoparasitism in uloborid spiders. Vincent (1974) suggested a simple method for rearing spiders in the lab conditions. Whitcomb & Eason (1965) proposed a crude method for the rearing of lynx spiders in lab condition. Downes (1981), Head (1995) and Prenter et al. (1997) studied the sexual dimorphism and differential mortality in grass land spiders of northern Europe. Marshall & Gittleman (1994) studied the relation between body size and clutch size in lycosid spiders. Dippenaar-Schoeman et al. (1989) and Haddad & Dippenaar-Schoeman (2002) studied the ecology, phenology and biology of termite eating spiders of the family Ammoxenidae in Africa.

Feeding behaviour: Warren et al. (1967) observed that the hungry spiders tend to kill everything offered as food but do not always eat all the prey they kill. Whitcomb & Eason (1967) studied the feeding behaviour of Oxyopes salticus. The hunting behaviour of salticid spiders consists of orientation pursuit, crouching, attachment and jumping (Gardner, 1964). The capture of the prey by lycosid spiders is marked by vigour and power. The spider pounces upon its victim and holding the body in its front legs, bites and crushes with its stout chelicerae (Gertsch, 1949).

Bradoo (1982) studied the feeding behaviour of Stegodyphus sarasinorum of the family Eresidae. The feeding behaviour of the members belonging to the family Uloboridae consists of a sequence of various behavioural units which lead from the detection of the prey to its possible use and consumption. These behavioural units are mostly similar to other orb-weavers (Robinson & Olazarri, 1971). Nentwig (1988) studied the web size and prey capture efficiency in linyphiid and theridiid spider space webs. Blackledge (1998) studied the behaviour of spiders towards the prey in their webs. Craig & Bernard (1990) studied the effect of web decoration for the attraction of insect prey. Eberhard (1990) conducted a detailed study on the functions of different parts of spider webs and proposed a classification pattern.

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Lubin (1986) studied the details of web building and prey capture efficiency in spiders of the family Uloboridae. Amalin et al.(1999) studied the survival of the spider Hibana velox raised on different artificial diets. Uetz & Stratton (1992) conducted a comparative study on survivorship of wolf spiders on different types of diets. Peck & Whitcomb (1968) try to rear spiders on artificial diet. Oraze & Grigarick (1989) studied the biocontrol potential of Pardosa ramulosa on leaf hoppers of Californian rice fields. The review of Riechert (1984) summarized the ecological significance of spiders for biological control of insect pests and balance of the ecosystem functions. Rypstra (1985) studied the effect of prey availability on the aggregation of spiders. Smith Trail (1980) studied the feeding behaviour of Argyrodes on solitary and communal spiders. Nakamura (1987) studied the effect of hunger and starvation on feeding potential of spiders in agroecosystems. Tso (1996), Blackledge (1998) and Blackledge & Wenzel (1999) studied the stabilimentum variation and foraging success in orb weaving spiders and explored the defending and attracting mechanism due to stabilimenta.

Brown (1981) studied the foraging ecology and niche partitioning in orb weaving spiders. Eberhard (1986), Herberstein & Heiling (1998) and Herberstein et al. (2000) studied the influence of web architecture on the capture efficiency of orb web spiders. Miyashita (1997) studied the factors affecting the difference in foraging success in three coexisting Cyclosa spiders. Pasquet et al. (1994) revealed the changes in web building behaviour of Zygiella x-notata due to the presence of potential prey in the vicinity of web. Rypstra (1997) and Blackledge & Gillespie (2002) investigated the prey capture efficiency in different kinds of orb webs. Studies of Sherman (1994) proposed that the shape and size of orb web express the spiders dynamic foraging and reproductive strategies.

Zschokke (1999) proposed a system for the classification of orb webs based on the feeding behaviour. Sunderland & Topping (1993) and Sunderland & Samu (2000) studied the biocontrol potential and population fluctuation of money spiders on agroecosystem insect pests. They also reviewed the effects of agricultural diversification on the abundance, distribution and pest control potential of spiders. Oedekoven & Joern (2000) opinioned that habitat quality can affect feeding potential of spiders on insect pests associated with plants. Studies of Kajak et al.(1968) revealed that presence of spiders can reduce the crop damage due to the attack of grasshoppers. Oedekoven (1996) studied the feeding potential of spiders on common grasshoppers of agroecosystems and analyzed the influence of wandering spiders on them. Redborg & Redborg (2000) observed the pattern of resource partitioning in spider community grass lands. Snyder & Wise (2001) reported the contrasting


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trophic cascades generated by the community of generalist predators in agroecosystems.

Hayes & Lockley (1990) observed the nocturnal activity and prey feeding behaviour in lycosids of cotton fields. Nyffeler et al., 1994; Snyder, 1999 and Snyder & Wise, 1999 studied the importance of spiders in ecological balance of insect pests in agroecosystems. Rosenheim et al. (1995) reviewed the theory and practice of intraguild predation among biological control agents in agroecosystems. Tuntibunpakul (1999) studied the impact of spiders on the abundance of insect pests and yield in soybean and vegetable agroecosystems in US. Airame & Sierwald (2000) studied the hunting and feeding behaviour of giant crab spiders in rain forest of Borneo. Tanaka (1984) estimated the feeding potential of kleptoparasitic theridiids on its host spider. Whitehouse (1988) studied the factors of host selection in kleptoparasitic spiders of the family Theridiidae and their feeding behaviour and intraspecific relations. Hurd & Fagan (1992) studied the prey preference and feeding potential of common grass land wolf spiders with special emphasis on cannibalism and microhabitat selection. Henschel (1994) studied the biology, diet and foraging behaviour of giant crab spiders of Namibian dunes.

Studies have been carried out by many workers on the sperm induction, courtship, mating and cocoon spinning behaviour and phenology of several species of spiders.

Sperm induction: Sperm induction is a characteristic of all male spiders. Bradoo (1975) studied the sperm induction of Stegodyphus sarasinorum.Later, Patel & Bradoo (1986) studied the sperm induction of Uloborus ferokus as part of their intensive study on the biology of the same species. Sperm induction of Philodromus rufus of the family Thomisidae has been studied by Dondale (1964). Similarly, Savory (1928) studied the sperm induction in Xysticus cristatus. Patel & Pillai (1987) documented the sperm induction in Latrodectus hasseltii and reported that it involved inductional movements, sperm web construction, sperm drop deposition and palpal charging.

Courtship behaviour: Courtship behaviour in spiders has been extensively studied by many workers. Evolutionary studies of this behaviour has been made by Platnick (1971) and Robinson & Robinson (1978). A comparative study on courtship behaviour of tropical araneid spiders was made by Robinson & Robinson (1980). In some spiders, chemoreception is sufficient to induce courtship, in others touch seems to be necessary (Nappi, 1965; Vlijm & Dijikstra, 1966; Bhatnagar et al.,1971; Rovner, 1971). The courtship behaviour of three species viz, Amaurobius ferox, A. similes and A. fenestralis was described by Locket

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(1926), Cloudsley- Thompson (1955) and Bristowe (1958) respectively. Kraft (1978) recorded the vibratory signals sent by the male of the above species in the female’s web as a means of communication during courtship. Jackson (1979) has done an elaborate study on the pattern of courtship behaviour in Dictyna and Mallos species of the family Dictynidae. The male of Uloborus ferokus performs some “intention movements” before courtship (Bradoo, 1982; Patel & Bradoo, 1986). As in other orb-weavers (Platnick, 1971; Robinson & Robinson, 1978) males of Uloborus ferokus spin a courtship mating thread in the female’s web. The courtship of Dysdera is a swift and unelaborated affair, relying entirely on tactile or chemotactic stimuli (Gerhardt, 1933). Jackson & Pollard (1982) studied the courtship behaviour of Dysdera crocata. In lycosid spiders, highly developed courtship behaviour is observed. A typical courtship movement of lycosid spider was observed in Pardosa crassipalpis (Schimidt, 1957). An elaborate description of courtship behaviour of P. amentata was given by Schimidt, 1957; Bristowe, 1958 and Vlijm et al., 1963. Kaston (1948) studied the influence of stimuli in the courtship movements of some vagabond (lycosid) spiders. The general pattern of movements of the male to the female of P. amentata was described by Vljim & Dijikstra (1966). In P. amentata, after the diminution of the distance from the female partner, the courtship gradually changed to the mounting behaviour but in P.lugubris some discontinuity was observed in between the courtship movement and mounting. Gavarra & Raros (1975) studied the courtship behaviour of some lycosid spiders. Stratton & Lowrie (1984) and Uetz & Stratton (1992) reported the production of sound by the male of Schizocosa oreta and S. rovneri during courtship. The courtship behaviour of Oxyopes salticus was studied by Whitcomb & Eason (1967). Courtship pattern of three species of Phidippus, P. apacheanus, P. clarus and P. coccineus have been described by Gardner (1965). Males of all these species perform a courtship dance. Males of P. johnsoni employ three different mating tactics depending on the type of female (adult, or sub adult, inside or out side nest) encountered (Jackson, 1978). The courtship versality of the types documented for P. johnsoni was also found in species of Myrmarchne (Jackson, 1982). Many of the behavioural elements performed by Myrmarachne lupata were found to be similar to those of P. johnsoni (Jackson, 1977), P. fermoratus (Jackson, 1982), Portiafimbriata (Jackson, 1982) and Mopsus mormon (Jackson, 1983).

Male of Latrodectus hasseltii perceives the presence of the female by chemoreception through the chemicals or pheromones present in the threads of the female’s snare (Patel & Pillai, 1987). The courtship behaviour of Misuminops celer has been studied by Muniappan & Chada


Ph. D. Thesis 145

(1970). This spider exhibits very little premating activity as compared to the members of the family Salticidae and Oxyopidae.

Mating behaviour: Jackson (1979) studied the mating behaviour of Dictyna and Mallos sp. of the family Dictynidae. Bristowe (1958) reported that the males of D. arundinacea construct a special “chamber” or mating canopy presumably similar to the nest of M. trivittatus and D.calcarata. The mating behavioural elements of M. trivittatus, D. arundinacea, D. calcarata and D. tridentate are similar to those observed in other species of Dictynidae and species of the closely related family Amaurobiidae (Montgomery, 1903; Berland, 1916; Gerhardt, 1925; Locket, 1926; Billaudelle, 1957; Bristowe, 1958; Gregg, 1961). Patel & Bradoo (1986) studied the mating behaviour of Uloborus ferokus. Sadana (1972) studied the mechanics of copulation in Lycosa chaperi. Gavarra & Raros (1975) reported the mating behaviour of some lycosid spiders. Mating behaviour of Oxyopes salticus was studied by Kaston (1948) and Whitcomb & Eason (1967), that of O. heteropthalmus by Gerhardt (1933) and Peucetia viridans by Whitcomb & Eason (1965). Accordingto Kaston (1936) the female Philodromus vulgaris produces a substance which stimulates the male for mating. In most of the species the males are found to be polygamous. Dondale (1961) studied the mating behaviour of Philodromus rufus. Muniappan & Chada (1970) studied the mating behaviour of Misumenops celer.

Cocoon spinning behaviour: Gertsch (1949) and Whitcomb et al.(1967) gave an elaborate description of cocoon formation in spiders belonging to the family Amaurobiidae. Bradoo (1972) studied the cocoon spinning behaviours of Stegodyphus sarasinorum. Patel & Bradoo (1980) described the mechanism of cocoon spinning along with maternal care in Uloborus ferokus. Schneider et al. (2000) studied the egg laying sequences and cocoon construction in Nephila clavipes. Schmidt (1957) studied the cocoon spinning behaviour of Pardosa crassipalpis. Gavarra & Raros (1975) studied the cocoon spinning behaviour of some lycosid spiders. Whitcomb & Eason (1967) observed the cocoon spinning behaviour of Oxyopes salticus and that of Misumenops celer by Muniappan & Chada (1970). The cocoon spinning behaviour of Latrodectus hasseltii has been studied by Baerg (1923), Cariaso (1967), and Patel et al. (1987). According to Baerg (1923), L. hasseltii and L. mactans constructed 4 egg sacs in every two weeks. Lawson’s study (1933) was in conformity with this.

Phenology: At the beginning of the 20th century the conventional wisdom about araneomorph spider life-cycles was that most were annuals, either spring breeders or summer-autumn breeders (Buddle, 2000). Cloudsley-Thompson (1955) concluded that individuals of all

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three British species of Amaurobius lived for about two years, overwintered twice, and spent their second winter as adults. Dondale’s (1961) seminal work presented quantitative data for five species of spiders in Nova Scotia, Canada. Head (1995) studied the features of selection on fecundity and variation in the degree of sexual size dimorphism in spiders. Kotiaho et al. (1996) studied the effect of sexual size on viability in wolf spiders. Legrand & Morse (2000) studied the factors driving extreme size dimorphism in spiders under low density. Jocque (1981) studied the influence of ecotone in size of spiders with explaining mechanisms and ecological significance of sexual size dimorphism. Buddle (2000) reported the life-cycle of Pardosa moesta inAlberta. Zimmerman & Spence (1998) and Buddle (2000) reported life-cycles of lycosids and a pisaurid from central Alberta.

3. 3. Materials and Methods

Spiders were collected from the fields for laboratory rearing. Adult spiders were reared singly in transparent plastic containers (6.5 cm x 5.9 cm) since they have cannibalistic behaviour. During the first 3-4 instars, the spiderlings were reared in transparent plastic tubes (5.2 cm x 2 cm). Later, the spiderlings were transferred to bigger, transparent plastic tubes (6.5 cm x 5.9 cm) till their maturity. For spiderlings of web builders, the bottom ends of the tubes were provided with pebbles for the attachment of threads. Moistened wad of cotton was provided in the containers at all stages of development for maintaining humidity and for availability of free water. The relative humidity was maintained from 60% to 80% throughout rearing. Temperature was maintained between 35o-38o C. Spiderlings were regularly fed on Drosophila melanogasterMeiger. Individual spiders were fed by dropping live prey into the containers. The food remains and excreta were removed everyday and the cotton removed every alternate day to prevent fungal growth. Spiderlings were measured after every moult to record the growth. The change in the colouration and ornamentation were also observed as the spider matured. Egg cases collected from the field and those constructed in the laboratory were teased open and the eggs were counted. Observation of different instar duration was also recorded. Penultimate or sub-adult males and females collected from the fields and from the laboratory stocks were isolated prior to their final moult for their reproductive behaviour studies. Courtship, mating and cocoon spinning behaviour of predominant spiders were studied. Behaviour associated with feeding and web construction was studied both in the laboratory and the field condition by extensive observations.


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The criteria to determine a juvenile as a sexually differentiated male was the presence of (slight) swollen palps, while the presence of two (sometimes very small) reddish dots in the central part of the epigastric fold was used to assign an individual as a sexually differentiated female. To determine the size of the spiders, the carapace width was measured at its widest point (Alderweireldt & Maelfait, 1988), using a graticule eyepiece fitted to a stereomicroscope.

3. 4. Results

Biology of the dominant spiders in Kuttanad rice agroecosystem:

1. Araneus ellipticus (Tikader & Bal) - Family: Araneidae This spider is found with its perfect orb web attached to the

leaves of upper canopy of the rice plant. It prepares the retreat in longitudinally rolled green leaves near the web where it is positioned except while feeding. A silken thread is attached to the retreat from the web to know the presence of prey in the web. A. ellipticus is active only during dusk.

Feeding behaviour: A. ellipticus devours all sorts of arthropods which are entangled

in its web. Since these spiders have very poor vision, they locate their prey by feeling the vibrations and tension of threads of the web. As the prey comes in contact with the web, the disturbances quickly reach the retreat by the warning thread which brings the spider to the spot. The spider bites the prey and then immobilizes it by wrapping the prey in silken threads. It quickly turns the prey with its legs and simultaneously their fourth legs pull out silk from spinnerets, which is used to wrap the victim. The spider consumes the prey by sucking the body fluids. The prey is bitten before being dragged to the hub or to the retreat, where the prey is sucked. Inedible objects are cut out of web and dropped to the ground.

Reproductive behaviour: Sperm induction: After the final moult, male prepares a

horizontal triangular sperm web attached to the green leaves near the retreat or side wall of the rearing chamber for sperm induction by the speedy up-and-down movements of the abdomen. After the completion of the sperm web, the male moves to the centre of the sperm web with its ventral side in an upside down position. This is followed by speedy up-and-down movements of the abdomen which results in the deposition of a drop of semen with gelatinous matter in the centre of the sperm web. Then it moves back and takes rest for a few seconds. The palps are then

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charged alternately by bringing them to the sperm drop. It takes 4-8 minutes for charging the palps.

Courtship and mating: Due to its poor vision, the male announces its presence by plucking the threads of the female web. After this ritual, he enters into the female snare. Courtship begins by moving over the snare with outstretched and vibrating palps. The female recognizes the presence of male in her snare through the vibrations. If the female is receptive, she responds to the male by approaching him and expresses her receptiveness by stretching the front pair of legs. Unreceptive female, on the other hand, shows an aggressive behaviour similar to that of attacking the prey. Courtship lasts for 30-40 minutes. After courtship, the male moves over the female from the side. Both male and female face each other for a few minutes and then the male moves to the side of female. The male rotates the female to an upside down position and grasps her legs and then touches the female epigynum with his outstretched palps (Fig. 3. 1). The entire palp moves in a semicircular fashion on the face of the epigynum. The left and right palps are inserted in to the epigynal orificealternately. The palpal insertion repeats for 5-7 times. Mating altogether lasts for 25-45 minutes. The male then releases his firm grasp and runs away from the female’s vicinity. After mating, the female continues in that position for some time and then moves deep into the retreat.

Cocoon construction: The female begins to prepare the cocoon 5-8 days after the mating. Hanging from a silken thread attached to the side of the container, it constructs a silken patch with the aid of the spinnerets and the last pair of legs. After constructing a dome like roof, it hangs below it with the ventral side up and legs clinging to the crescentic edge of the dome. After finishing the dome like structure, it forces the eggs into the centre of the dome with a gelatinous material. Then it spins loose threads across the eggs and covers the eggs rapidly, encloses the


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eggs in a spherical shaped enclosure and then produces a fluffy mass of silk having no perfect outline. It takes about one hour to complete the construction of the cocoon. One female constructs 3-5 cocoons during one cropping at an interval of 3-5 days. The average number of eggs in each cocoon varies; the first with an average of 108 eggs with a minimum of 75 and a maximum of 116. The female lays an average of 78.7 eggs in one season.

Life history:The spiderlings emerge out from the cocoon after 7-10 days of

incubation. First moult occurs inside the cocoon itself. The transparent second instar spiderlings emerge out from the cocoon through a small hole at the side. They remain on the mother’s snare for a few days and disperse by ballooning. Females take 9 moults and males take 8 moults to attain maturity. The longevity period of female and males are 236.27±13.91 and 198.74±24.82 days respectively. It is also noticed that as the spiderlings become mature, they go on changing their web-building patterns. Instar duration, growth rate with length and width of carapace and total length of body at each instar of female and male is given in Table 3.1. and 3. 2. respectively.

Phenology:Mature spiders are found numerously in the field from the fifth

week of the crop growth. Reproductive males and females can be collected from the retreat on daytime also. They show a typical population fluctuation pattern like other web building spiders as shown in Figure 3. 2.

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Figure 3. 2. Phenology of Araneus ellipticus

0

50

100

150

200

250

1 2 3 4 5 6 7Fortnight

Num

ber

Male Female Juvenile

2. Pardosa pseudoannulata (Bosenberg & Strand) -Family: LycosidaeThis is a hunting spider and does not construct any web except

the sperm webs. These spiders can be seen on the foliage of rice plants in search of prey. They can also be found under dry leaves and soil crevices. P. pseudoannulata can also actively move over the surface of water and is a fast swimmer which can even dive deep into the water. The spiderlings actively forage below the lower half of the rice plant. Numerous spiderlings can be found in the final stage of the crop growth. The mating pairs can be seen in the field even during bright daylight. When disturbed, they withdraw themselves into the interior of the plants.

Feeding behaviour: P. pseudoannulata feeds on a wide range of insects within its

reach. As it does not spin any web, it solely relies upon its speed and vigour for capturing prey. When a prey is introduced into the rearing chamber, the spider approaches the prey with great speed and touches it with the first pair of legs. If the prey tries to move, the spider overpowers it with its strong chelicerae and front legs. It then bites the prey on its head region and keeps the prey immovable by pressing with the legs. Once keeping the prey stationary, the spider sucks its body fluids and gives up the exoskeleton as a small mass with some fluid secretions. P. pseudoannulata normally takes 10-15 minutes to suck the fluids of green leaf hopper and more time for bigger preys.


Ph. D. Thesis 151

Reproductive behaviour Sperm induction: Following the final moult, the male prepares

a delicate rectangular sperm web attached to green leaves in the field and to the surface of the rearing bottle in the lab. After the completion of the sperm web construction, it takes rest for a few minutes. After rest, it rubs the abdomen against the sperm web. Rubbing for 5-6 times results in the deposition of a small drop of gum like gel in the centre of the sperm web about a few millimeters in diameter. Then it moves forward and turns back to the drop of semen. Afterwards, it touches the palp into the centre of the drop, each palp dipping into the drop alternately many times within a time span of 10-15 minutes. After palpal charging, the male spider starts searching for females.

Courtship and mating: The male recognizes the presence of the female by sight. It welcomes the female by raising the palps and front pair of legs. Then it stretches its body longitudinally to the maximum possible. The male then approaches the female by holding the palps in an upright position. This is a very cautious movement expecting sudden attack from the female. Every movement is with careful watching. Finally, the male reaches the front of the female and stays there opposite to the female. He then touches the palps or front legs of the female by very slow movement of its own first pair of legs. The receptive female allows this touching, but the unreceptive ones try to attack the male or runs away. Then the male mounts over the female from side to her cephalothorax. The male then touches the abdomen of the female by each pair of legs. The mating pair then rotates themselves three to four times resulting in a position with the female having its ventral side up and with the male over it. After careful movement of the legs, the male grasps each leg of the female by its outstretched legs. He then moves its palps over the surface of the epigynum three to four times and then inserts the right palp into the genital orifice followed by the left palp (Fig. 3. 3). This process repeats for 10-15 minutes within a period of 20-30 minutes. After the final palpal insertion, the male releases each of his legs from the body of the female and runs away within a few

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seconds. The female then comes to the normal position and remains in this position for a few minutes.

Cocoon construction: Cocoon construction starts after 3-5 days of mating. The gravid female prepares a creamish-white circular mat of closely woven silk and then makes the rim concave with a series of rapid strokes made up of downward movements of the abdomen. She then deposits some eggs with a gel like matter in the centre of the concave sheet. After this, she touches the tip of her abdomen to the side of the rim and starts to cover the eggs deposited by spinning silk vigorously back and forth across the egg mass. This speedy movement of the abdomen helps to cover the egg mass in 10 to 15 minutes. Then the upper and lower halves of the egg sac are pasted together with a special silk produced by circular movements across the egg sac. After completion, she attaches it to her spinnerets by bending the tip of the spinnerets to the side of the egg sac and carries it up to hatching. Usually one female prepares two to three cocoons during one crop season with an interval of 30-35 days. Higher numbers of eggs are found in the first cocoon and the number decreases subsequently. The average number of eggs in the first cocoon is 131.28 with a minimum of 123 and a maximum of 144 eggs. The second cocoon has an average of 113.41 eggs with a minimum of 89 and a maximum of 123 eggs.

Life history: Normally eggs undergo 15-20 days of incubation. At the end of

this period, the spiderlings emerge out through the perforation made by the mother along the side of the egg case. The first moult occurs within the egg sac. The newly hatched spiderlings crawl over the mother’s abdomen. After 4-6 days, the spiderlings disperse by ballooning. First few instars are creamish white in colour. The colour then changes to an ash tinge as the age advances. Females take 10 moults and the males take 9 moults to attain maturity. The males take an average of 158.19±6.15 days to attain maturity and the females take an average of 218.48±7.61 days. Instar duration and growth rate with length and width of carapace and total length of body at each instar of female and male is given in Table 3. 3. and 3. 4. respectively. Males have an average life span of 219.61±18.67 days with a minimum of 48 days and a maximum of 72 days of adult life. Females have longer life span than that of male with an average of 319.72±15.23 days with a minimum of 84 days and a maximum of 112 days of adult life.

Phenology:Numerous spiderlings can be found from the start of the crop.

Mature spiders can be found at the middle stage of the crop growth. Numerous courting pairs and females with cocoons are present as the


Ph. D. Thesis 153

crop growth advances. New generation spiderlings are numerously present at the final stage of crop growth. Like other members of this family, these spiders also show population fluctuations as shown if Figure 3. 4.

Figure 3. 4. Phenology of Pardosa pseudoannulata

0

50

100

150

200

250

1 2 3 4 5 6 7

Fortnight

Num

ber


3. Tetragnatha mandibulata Walckenaer - Family: TetragnathidaeThis spider is found with its perfect orb web attached to the

leaves of upper canopy of the rice plant. Generally the webs are parallel to the ground and act as an umbrella like layer over the plants. This spider rests on the rice stem or under leaves with its first two pairs of legs stretching forward and the back pairs stretching backwards, thus making it extremely difficult to locate the spider in the field. Any disturbance in the web attracts the resting spider into the web. It can also be often seen in an inverted position in the centre of the web.

Feeding behaviour: The movements of the trapped insects drive the spider into the

web. It suddenly produces swathing silk from the spinnerets and covers the prey with this silk. It then holds the trapped prey with its first two pairs of legs and then jets a stream of silk targeting the insect trapped. By rotating prey with its front legs, it entraps the prey in silk covering. It then sucks the body fluids and finally gives up the exoskeleton as a dry ball. If excess insects are trapped, these are kept preserved in the web itself by injecting a preservative enzyme by a single bite on the prey.

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Reproductive behaviour: Sperm induction: Male prepares a triangular sperm web in the

side wall of the bottle. First of all, it creates a line of silk across the container and then makes many close silk threads on one side by rapid movements of the abdomen. After the completion of sperm web, the male spider deposits a small drop of fluid in the centre of the sperm web on the upper side. Then the palps are charged alternately. The process of palpal charging is repeated for 5-10 minutes.

Courtship and mating: In the field, courtship and mating occurs in leaf blades or flower bunches of rice plant. Occasionally, mating pairs can be found on the web. Males position themselves at the edge of a female’s web and make slight leg movements on the strands of the web. They often tap the silk for a few seconds, pause with their first pair of legs resting gently on the web strand, and then repeat the behaviour until the female responds. The female almost instantly orients to the male’s vibrations and vibrates the web in response. The male comes in the opposite direction (face to face) of the female. The male and female touch each other with the first pair of legs. Unreceptive female tries to attack the male during this time. Receptive female does not show any reaction to the male’s activity. After 5-10 minutes, the male comes closer to the female and they touch each other with the jaws. The male tries to open the cheliceral fang of the female with his own fangs. They then cross the jaws for 20-30 minutes. After this, the male suddenly withdraws his jaws and female comes to a position with her ventral side up. The male again opens the cheliceral fangs of the female with his fangs and locks her legs with his own legs. After crossing their jaws again, the male touches the epigynal region of the female with his palps. In response, the female curves her abdomen longitudinally. This helps the male to open the epigynal orifice and he introduces his palps into the epigynal opening (Plate 3. 1). The palps are introduced alternately into the epigynal orifice for 4-5 times. During this process, both the male and female vibrate their body very rapidly. After 10-15 minutes on


Ph. D. Thesis 155

completion of mating, the male closes the epigynal orifice by a white coloured resin plug by a material secreted from his palp. This material elongates out as a projection from the epigynum.

Cocoon construction: Female begins to prepare the cocoon 4-9 days after mating. She selects a healthy green leaf or flower bunch for cocoon construction. She prepares a longitudinal platform on the leaf blade or a circular platform on the side wall of the rearing bottle. The platform is constructed by the vertical movements of the abdomen. The platform is constructed within 10-15 minutes. After completion of the platform, it forces her eggs into the centre of the platform with a gel like material. It then spins fine threads across the eggs and covers the eggs rapidly. Afterwards, it encloses the eggs in this tough silk layer and spins an outer covering of loose silk fibres. The entire process completes in 30-45 minutes. One female constructs 2-4 cocoons in one crop season with an interval of 7-15 days. The average number of eggs in each cocoon varies; the first with an average of 68.25±8.52 with a minimum of 42 to a maximum of 76.

Life history: Spiderlings emerge out from the cocoon after 6-12 days of

incubation. The first moult occurs within the cocoon itself. The transparent second instar spiderlings emerge out from the cocoon through a small hole at the side. They remain on the mother’s snare for a few days and disperse by ballooning. Females take 9 moults and males take 8 moults to attain maturity. The longevity period of females and males are 230.47±11.19 and 187.05±10.98 days respectively. It is also noticed that as the spiderlings become mature, they go on changing their web-building patterns. Instar duration and growth rate with length and width of carapace and total length of body at each instar of female and male is given in Table 3. 5. and 3. 6. respectively.

Phenology:Mature spiders are found in the field from the fifth week of the

crop growth. Reproductive males and females can be collected from the retreat on daytime also. They show a typical population fluctuation pattern like other web building spiders as shown in Figure 3. 5. The comparative phenology of these three dominant spiders is shown in Figure 3. 6.

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156

Figure 3. 5. Phenology of Tetragnatha mandibulata

0102030405060708090

1 2 3 4 5 6 7

Fortnight

Num

ber


Figure 3. 6. Comparative phenology of three dominant spiders

0

50

100

150

200

250

300

350

400

1 2 3 4 5 6 7Fortnight

Num

ber

A.ellipticus P.pseudoannulata T.mandibulata


Ph. D. Thesis 157

3. 5. Discussion

Feeding behaviour:There are numerous studies on the feeding behaviour of spiders

(Nyffeler & Benz, 1981). Spiders are generally considered to be polyphagous predators (Roth, 1993). After the spider secured its hold, the prey was quickly pulled toward the spider’s body. Thereupon the chelicerae of the spider’s fangs moved apart and were inserted quickly into the nearest part of the victim’s body. Immediately after the bite, the tips of the legs released their grip and the prey was held in the air only with the chelicerae. This behaviour appears to minimize any danger to the spider from the prey. Holding the prey aloft is advantageous to the spider because the victim cannot apply any force against the substrate to free itself. In the laboratory study it was observed that the three species of spiders started to feed on insect’s larvae during their 2nd instar. This is not surprising since spiders, after moulting into the 2nd instar stage, are generally found to be self-sufficient (Foelix, 1996). At this stage, they have developed their sensory hairs, their legs are equipped with the typical claws, they have bulging eyes, and their mouthparts are already differentiated sufficiently for capturing and feeding on prey. Then, the consumption increases, as they develop to later instar stages. During the intermoult intervals, spiderlings require ample food to enable them to develop into the next stage (Foelix, 1996). However, feeding slowed down before moulting. This occurs naturally in all spiders. Foelix (1996) stated that most spiders that were preparing to moult withdraw into their retreat for several days and stop feeding. Uetz (1991) reported that certain spiders must feed on a variety of insect prey species to obtain the optimum nutrition for survival.

Phenology:Knowledge of cyclic temporal aspects of organisms’ life cycles

(phenology) is crucial for understanding population dynamics and community ecology, and lends realism to evolutionary and ecological hypotheses (Tauber & Tauber, 1981). This basic data can be time-consuming to obtain, as it requires sampling a population repeatedly throughout the year, and phenology may vary geographically or from one year to the next. Draney (1997) found evidence that the phenology patterns of individual taxa vary among the habitats, so it can be assumed that species are either univoltine or multivoltine, regardless of the habitat they occupy. Eurychronous spiders would be capable of reproducing opportunistically when the habitat is favourable or when they arrive at a favourable habitat. While the habitat remains favourable, continuous reproduction allows for individuals to maximize their instantaneous rate of reproduction and thus, probably, their fitness. It is interesting to note

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that Samu’s (1998) phenological study of 90 linyphiid species found that all eurychronous species were ‘‘common aeronauts,’’ species commonly observed or collected ballooning. Stenochronous species, conversely, appear to be phenological ‘‘specialists,’’ finely adapted to completing various life history stages at specific times when conditions are most favourable, or to avoiding unfavourable conditions.

In wolf spider populations, considerable variation can be observed in phenology, growth rate, adult size and reproductive output (Alderweireldt & Maelfait, 1988; Simpson, 1993; Maelfait & Hendrickx, 1998; Samu et al., 1998; Buddle, 2000). The variation and covariation of these traits is of particular importance to understand the costs and benefits of a specific life history trait (Stearns, 1992; Roff, 1992) and can be used to predict changes in life history patterns when environmental conditions change. The life-cycle of a field population of lycosid in Denmark has already been analysed by Toft (1999), who demonstrated that adults of this species appear in spring and females produce one or (possibly) two egg sacs in summer. The hatched juveniles grow during summer and autumn and overwinter as sexually differentiated juveniles or sub adults. Laboratory experiments conducted by Buddle (2000) revealed that temperatures as well as photoperiod are important factors that determine growth and development of these spiders. It is likely that the group of smaller juveniles originates from a second egg sac produced by the females (Toft, 1999) and also it is likely that these larger individuals overwintered twice before reaching the adult stage (Alderweireldt & Maelfait, 1988).

The movement of spiders between habitats is critical for the build-up of their populations. After rice has been transplanted, a number of wolf spiders moved into neighbouring rice fields and significantly increased the population density of spiders there. However, most spiders in the rice fields moved back to the bunds of the field after harvest and then overwintered here. Most spiders were killed by insecticide spraying during the early stage of the rice crop, thus reducing predation of insect pests. Besides pesticides, other human practices that can disrupt spider populations are mowing, plowing, harvesting, and crop rotation (Marc etal., 1999). Soil disturbance by plowing destroys overwintering sites and can kill any spiders already present in the soil (Marshall & Rypstra, 1999). The movement of farm equipment through a crop field damages spider webs and may destroy web attachment sites (Young & Edwards, 1990).Consequently, spider density and diversity is higher in organic fields than in conventional ones (Marc et al., 1999). Clearly, human input is harmful to spiders, and the best spider conservation strategy may be non-intervention (Young & Edwards, 1990).


Ph. D. Thesis 159

Reproductive behaviour: Among the web-building spider, Araneus ellipticus, the

courtship behaviour starts as soon as the male enters the female’s web. This supports the existence of air-borne sex pheromones in the silken threads as reported in several other families of spiders (Olive, 1982; Patel & Pillai, 1987). Apart from these chemical communications, vibratory signals also play an important role in courtship and mating among the web building spiders (Witt, 1975; Kraft, 1978). It is presumed that the body vibrations and palpal drumming may produce an audible sound in order to communicate with the female. Elaborate courtship displays by male spiders generally function to suppress the females’ predatory behaviour toward the males (Foelix, 1982).

Copulation sometimes follows the contact behaviour or non-contact behaviour. The contact behaviour includes stroking with palps and legs of sexual partners, thus making a physical contact with each other. Interactions normally begin with non-contact behaviour such as plucking of the web and the female charging or lurking toward the male. In most of the spiders, vision seems to be of little or no significance. It can be presumed that communication is primarily by means of vibratory signals transmitted through the silk threads during non-contact behaviour and by tactile and chemotactic signals during contact behaviour.

The vibrations of the female were either fast arrhythmic pulses or slower rhythmic pulses and seemed to predict her response to the male. When a female exhibited vigorous arrhythmic pulses, males approaching any further onto the web were chased away. Similar arrhythmic web vibrations were observed from a female as large prey became entangled in her web prior to her attack on the prey. Only when the female pulsed rhythmically could the male approach her without interference. More often, once a male made this initial contact with an accepting female, they paired immediately. In the case of tetragnathids, as the male approached, both sexes spread their chelicerae and fangs apart. Within seconds the pair vigorously grappled to interlock cheliceral fangs and assumed a ventral- to-ventral position for mating. The male used his third pair of legs to contact the female’s abdomen and often moved her into position, sometimes even shaking her until he successfully inserted his pedipalp. Once chelicerae were engaged, mating consisted of several alternating insertions of each pedipalp and was terminated by cheliceral disengagement. During each insertion, the male inflated the hematodochae of his pedipalp repeatedly.

In the three studied species, females terminated the mating processes. These terminations often occurred when the male was in the process of switching from one pedipalp to another. The female pressed her chelicerae together, bringing her fangs closer to the body of the male. The male used his 3rd pair of legs to press his body away from the female

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as she moved her chelicerae. Once the chelicerae were disengaged, the male quickly retreated from the web, while the female would remain where she had been mated. Sometimes, after mating, the female chased the male a short distance with her chelicerae and fangs spread open before returning to her former position. Occasionally, males were cannibalized after mating. Elaborate courtship displays by male spiders generally function to suppress the females’ predatory behaviour toward the males (Foelix, 1982).

Sexual conflict: The simplest case of intersexual conflict observed was males

attempting to mate with every female they encounter and protecting their sperm from rival males, whereas females attempting to mate with the best male only and rejecting others. For females, additional copulations beyond those necessary to fertilise the available eggs can be costly. The greater the cost to the female, the more vigorous will be the rejection of additional males. Females may reduce receptivity after one mating (Elgar, 1998). Conflict can occur also over the relative investment of the sexes in brood care.

The relative cost of mating for males is determined by a large variety of factors. In spiders, mature males usually leave their webs and search for sedentary females. Mate search is possibly very risky and energetically costly (Vollrath & Parker, 1992). Once mate search has been successful, it usually has to compete with other males for access to females. Males may fight against rivals and risk injury and possibly death (Robinson & Robinson, 1980; Whitehouse, 1997). Alternatively, males may invest a large amount of energy in courtship or signalling to impress choosy females (Lubin, 1986; Kotiaho et al., 1996; Mappes etal., 1996). In many species, females are sexually cannibalistic, which imposes another potential cost on the male. Generally, the value of a mating depends on the reproductive prospective that remains after one mating has occurred. This residual reproductive value of a male, i.e. his chance to find and inseminate another female, is a function of the operational sex ratio and the species (or population) specific combination of the above factors. In some instances, the costs of mating for males appear to be directly inflicted by the female's behaviour, as in the case of sexual cannibalism. In others such as male courtship and male provisioning of the female, it is not always clear if the behaviour is a direct response to the female's demands, but it is nonetheless a variable cost for the males.

Cocoon spinning:The cocoon spinning behaviour is a good example of succession

of instinctive responses controlled by both internal and external stimuli.


Ph. D. Thesis 161

The sequence of different behavioural stages such as the platform preparation, oviposition, and concealment of eggs follow one after the other and so organized that none of the stages is omitted or repeated again in normal course (Patel & Bradoo, 1986). It was observed that the abundance of food increases the production of greater number of cocoons and as such the number of eggs (Riechert & Tracy, 1975). The scarcity of food was found to be prolonging the time interval in between successive cocoon formation and the reduction in the silk production. This turn influences the complete concealing of the egg mass and also the production of number of eggs. Placing of cocoons just nearer or in the vicinity of the mother’s resting place, when they are not carried by the mothers, reduces the chances of predation.

Life history: Biological studies carried out in the laboratory reveals that the

number of instars varies among the species and sexes of the same species. The time taken to prepare the sperm web, its shape and size and the behavioural patterns associated with palpal charging were found to be different among different species observed in the laboratory as reported by Peck & Whitcomb (1968), Bradoo (1975) and Patel & Bradoo (1986). The results of the present study are in accordance with the results of previous studies conducted on the different aspects of life span in spiders. There is evidence that seasonality in the availability of prey causes variation in size for these spiders.

Tikader (1987) reported that in general, the number of eggs in a cocoon varied from 1-2000 but 100-300 is normal. Thang et al. (1988)reported that the wolf spider Pardosa pseudoannulata passed through 10 instars to reach adulthood, whereas Nirmala (1990) reported the presence of only eight instars. Berland (1932) reported that the purse-web spider Atypus was reported to survive for seven years, while large tarantulas lived over 20 years. Eckert (1967) reported that small spiders needed only a few moults (about five) whereas large spiders pass through about 10 moults to reach the adult stage. It was reported also that early nymphal stages may moult every few days, but later instars needed several weeks to prepare for the next moult. The number of moults could also be influenced by the availability of food.

The wide variation in size-range of life-stages seen in the present study has been reported for other spiders (Eason & Whitcomb, 1965 and Almquist, 1982). An extended period of recruitment would increase the number of instars occurring together, which would increase the size-range of life-stages. There may also be differences between early and late-hatched spiderlings. Almquist (1982) reported that later spiderlings tended to be heavier than earlier. On the other hand, Buddle (2000) said

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162

that later spiderlings were substantially smaller than earlier. Either way, size difference of new spiderlings will, to an extent, increase the spread of the size-range of subsequent life-stages, particularly of the immature ones.


Ph. D. Thesis 163

Table 3. 1. Duration (in days) of instars and changes in carapace length, width and total length (in mm.) of spider Araneus ellipticus (Tikader & Bal) reared in laboratory (average of 7 female individuals)

Number of days Length of carapace Width of carapace Total length Instars Range Mean±S.D Range Mean±S.D Range Mean±S.D Range Mean±S.D

II

III

IV

V

VI

VII

VIII

IX

Adult

07-12

11-18

09-14

13-17

12-18

14-24

11-22

10-18

98-123

10.28±1.06

15.85±1.11

11.85±0.62

14.14±0.57

16.71±1.18

18.42±2.07

15.71±2.52

14.71±2.76

111.42±10.4

0.40-0.50

0.72-0.80

0.84-0.95

0.95-1.15

1.25-1.45

1.65-1.85

1.93-2.12

2.15-2.45

2.35-2.60

0.43±0.03

0.75±0.02

0.89±0.04

1.04±0.07

1.33±0.06

1.74±0.02

2.05±0.08

2.28±0.13

2.49±0.09

0.25-0.40

0.50-0.65

0.65-0.80

0.80-0.95

0.95-1.02

0.98-1.10

1.15-1.30

1.45-1.62

1.70-1.83

0.33±0.05

0.59±0.05

0.72±0.04

0.88±0.04

0.98±0.02

1.03±0.05

1.24±0.05

1.55±0.63

1.77±0.05

1.62-1.71

2.22-2.35

2.68-2.79

3.42-3.62

3.95-4.12

4.26-4.41

4.53-4.78

5.15-5.62

5.65-5.83

1.67±0.03

2.29±0.04

2.72±0.04

3.79±0.27

4.02±0.07

4.35±0.05

4.65±0.09

5.40±0.19

5.73±0.07 Total developmental period of : 124.85±3.51 Total life span of : 236.27±13.91

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Table 3. 2. Duration (in days) of instars and changes in carapace length, width and total length (in mm.) of spider Araneus ellipticus (Tikader & Bal) reared in laboratory (average of 7 male individuals)


II

III

IV

V

VI

VII

VIII

Adult

05-11

10-14

11-14

12-17

10-18

12-16

08-17

73-102

08.42±0. 33

12.46±1.04

12.85±0.19

15.28±1.82

14.28±2. 10

14.57±1.69

22.85±2. 21

90.85±11.34

0.38-0.42

0.40-0.53

0.54-0.63

0.68-0.74

0.78-0.88

0.93-1.05

1.10-1.33

1.35-1.58

0.39±0.01

0.47±0.05

0.57±0.03

0.70±0.02

0.83±0.03

0.98±0.05

1.18±0.08

1.47±0.08

0.19-0.25

0.31-0.38

0.48-0.56

0.53-0.69

0.65-0.78

0.75-0.87

0.93-1.23

1.18-1.34

0.21±0.02

0.35±0.02

0.52±0.03

0.59±0.05

0.71±0.06

0.82±0.05

1.04±0.13

1.26±0.07

1.23-1.42

1.45-1.57

1.63-1.82

1.85-1.96

1.95-2.23

2.28-2.35

2.73-2.95

3.10-3.87

1.34±0.06

1.51±0.04

1.72±0.07

1.91±0.04

2.11±0.11

2.38±0.18

2.84±0.08



Ph. D. Thesis 165

Table 3. 3. Duration (in days) of instars and changes in carapace length, width and total length (in mm.) of spider Pardosa pseudoannulata (Bosenberg & Strand) reared in laboratory (average of 7 female individuals)


II

III

IV

V

VI

VII

VIII

IX

X

Adult

16-21

17-31

14-25

19-27

18-25

21-28

25-48

15-26

21-27

84-112

18.71±1.97

24.28±5.28

20.42±3.69

24.28±2.56

21.00±2.76

24.85±3.13

35.00±7.70

21.71±3.77

24.00±2.00

101.24±7.62

0.61-0.75

0.77-0.85

0.95-1.10

1.17-1.30

1.45-1.80

1.97-2.20

2.37-2.58

2.61-2.79

2.65-2.99

3.10-3.37

0.68±0.05

0.79±0.02

1.01±0.06

1.22±0.04

1.62±0.13

2.08±0.09

2.47±0.08

2.69±0.07

2.76±0.12

3.24±0.11

0.33-0.55

0.61-0.76

0.79-0.87

0.98-1.18

1.43-1.78

1.85-2.05

2.15-2.27

2.31-2.42

2.56-2.71

2.87-3.18

0.42±0.09

0.69±0.06

0.82±0.03

1.06±0.07

1.60±0.12

1.95±0.08

2.21±0.05

2.38±0.03

2.66±0.06

3.01±0.11

1.13-1.52

1.67-1.73

1.97-2.08

2.47-2.80

3.48-3.71

4.65-4.83

5.51-5.76

6.31-6.62

6.82-7.21

7.61-7.92

1.27±0.13

1.70±0.02

2.02±0.04

2.61±0.11

3.59±0.09

4.75±0.07

5.62±0.11

6.48±0.13

6.99±0.16


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Table 3. 4. Duration (in days) of instars and changes in carapace length, width and total length (in mm.) of spider Pardosa pseudoannulata (Bosenberg & Strand) reared in laboratory (average of 7 male individuals)


II

III

IV

V

VI

VII

VIII

IX

Adult

15-20

14-22

10-18

15-21

15-22

19-25

19-31

14-23

48-72

17.57±1.42

18.28±2.03

13.14±2.28

18.42±2.43

19.14±3.03

22.85±3.41

26.14±6.04

18.42±3.50

61.42±12.52

0.41-0.65

0.85-1.02

1.07-1.18

1.25-1.57

1.71-1.86

2.10-2.17

2.20-2.38

2.47-2.61

2.63-2.81

0.57±0.08

0.95±0.08

1.13±0.04

1.40±0.12

1.78±0.05

2.13±0.03

2.29±0.07

2.54±0.06

2.72±0.06

0.37-0.45

0.61-0.70

0.73-0.82

0.95-1.22

1.35-1.47

1.78-2.02

2.05-2.18

2.21-2.27

2.31-2.43

0.41±0.03

0.64±0.03

0.77±0.03

1.08±0.10

1.41±0.04

1.89±0.11

2.10±0.04

2.24±0.02

2.37±0.04

1.37-1.42

1.95-2.27

3.21-3.48

4.10-4.31

4.45-4.58

4.61-4.81

4.92-5.35

5.58-5.85

5.92-6.18

1.40±0.01

2.10±0.13

3.34±0.10

4.22±0.09

4.51±0.04

4.71±0.08

5.12±0.17

5.67±0.09

6.05±0.10 Totaldevelopmental period of : 158.19±6.15 Total life span of : 219.61±18.67


Ph. D. Thesis 167

Table 3. 5. Duration (in days) of instars and changes in carapace length, width and total length (in mm.) of spider Tetragnatha mandibulata Walckenaer, reared in laboratory (average of 7 female individuals)


II

III

IV

V

VI

VII

VIII

IX

Adult

06-12

14-21

16-20

11-16

15-21

12-18

12-16

16-21

90-111

08.71±1.45

16.14±1.49

18.71±0.73

14.02±0.25

17.14±1.41

16.71±1.44

14.42±0.75

18.14±1.34

100.14±6.93

0.70-0.81

1.25-1.53

1.68-1.82

1.88-2.04

2.13-2.28

2.44-2.56

2.58-2.82

2.98-3.17

3.43-3.62

0.73±0.10

1.38±0.05

1.72±0.03

1.98±0.12

2.21±0.07

2.51±0.11

2.76±0.04

3.08±0.05

3.51±0.07

0.43-0.56

0.85-0.1.04

1.18-1.26

1.37-1.52

1.52-1.58

1.73-1.79

1.81-1.88

1.91-1.99

2.02-2.23

0.52±0.01

0.98±0.01

1.21±0.01

1.42±0.03

1.54±0.02

1.74±0.05

1.83±0.08

1.95±0.06

2.14±0.04

0.86-0.97

2.28-2.42

3.85-4.22

5.32-5.52

5.95-6.14

6.87-7.16

8.32-8.61

8.92-9.13

10.43-10.62

0.94±0.05

2.34±0.07

4.11±0.04

5.48±0.11

6.07±0.13

7.10±0.18

8.53±0.05

9.02±0.23


Spiders of Kuttanad

168

Table 3. 6. Duration (in days) of instars and changes in carapace length, width and total length (in mm.) of spider Tetragnatha mandibulata Walckenaer, reared in laboratory (average of 7 male individuals)


II

III

IV

V

VI

VII

VIII

Adult

08-10

11-14

11-18

10-18

12-17

11-16

12-19

76-93

09.57±0.27

12.42±0.73

14.85±1. 47

13.85±1. 87

15.14±1.03

13.85±1.67

15.42±2.35

85.57±7.80

0.36-0.52

0.87-1.03

1.42-1.51

1.68-1.83

2.17-2.22

2.24-2.36

2.76-2.88

3.38-3.61

0.43±0.06

0.96±0.06

1.46±0.04

1.77±0.10

2.11±0.08

2.31±0.22

2.83±0.92

3.52±0.05

0.42-0.51

0.76-0.88

1.15-1.23

1.33-1.41

1.46-1.52

1.67-1.77

1.82-1.87

1.96-2.12

0.45±0.01

0.81±0.04

1.18±0.01

1.38±0.05

1.51±0.03

1.71±0.06

1.84±0.15

2.04±0.07

0.71-0.83

1.88-2.02

3.22-3.52

4.42-4.62

5.36-5.51

6.41-6.66

7.44-7.62

8.28-8.41

0.75±.09

1.93±0.13

3.43±0.09

4.57±0.11

5.46±0.23

6.58±0.22

7.53±0.26


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1 CHAPTER 1- Page 1-116 - Shodhgangashodhganga.inflibnet.ac.in/bitstream/10603/7156/15/15_chapter 3.pdf · Biology of dominant spiders Ph. D. Thesis 139 Chapter 3 BIOLOGY OF DOMINANT