Introduction to Mosquito Biology and Key North Texas species · Mosquito mouthparts . Modified from...
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Introduction to Mosquito Biology and Key North Texas species Michael Merchant, PhD, BCE Professor and Urban Entomologist Texas A&M AgriLife Center at Dallas [email protected]
Introduction to Mosquito Biology and Key North Texas species · Mosquito mouthparts . Modified from Scientific American, Tom Prentiss . Mosquitoes have piercing sucking mouthparts
Notes may be available in some Powerpoints to help clarify individual slides. Note that the information in these slides was developed for north Texas and may not be completely applicable to other parts of the state, or other states.
Mosquitoes: Culicidae 3,500 species worldwide Occur on every continent except
Antarctica. Most important arthropod affecting
human and animal health. Diverse habitats; some have become
“domesticated”. Hundreds of millions of dollars spent
on control in U.S. for nuisance reasons alone.
Courtesy G. Hamer, Dept. Entomology, Texas A&M University
Anopheles Malaria mosquito
219 million cases in 2010 (cf. 34 m AIDS cases) 660,000 deaths
annually 90% cases in
Africa $1.84 b
international aid
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Note that malaria used to be endemic to the US as late as 50 years ago. According to CDC, “The National Malaria Eradication Program, a cooperative undertaking by state and local health agencies of 13 Southeastern states and the CDC, originally proposed by Louis Laval Williams, commenced operations on July 1, 1947. It consisted primarily of DDT application to the interior surfaces of rural homes or entire premises in counties where malaria was reported to have been prevalent in recent years. By the end of 1949, over 4,650,000 house spray applications had been made. It also included drainage, removal of mosquito breeding sites, and spraying (occasionally from aircrafts) of insecticides. Total elimination of transmission was slowly achieved. In 1947, 15,000 malaria cases were reported. By 1950, only 2,000 cases were reported. By 1951, malaria was considered eliminated from the United States.” For more info, see http://www.cdc.gov/malaria/about/history/elimination_us.html
Recognizing Mosquitoes The fly order (Diptera) Family Culicidae long proboscis long legs scales on wing veins
172 species in U.S. 85 species in Texas 37 species in Dallas
County (DCHHS)
from Bohart and Washino. Mosquitoes of California
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Other insects commonly confused with mosquitoes include crane flies, lake midges, and fungus gnats.
Mosquito life cycle
eggs
larva
pupa
adult
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Typical generation times for mosquitoes last 10 to 14 days or more, starting with adults who feed 1-3 days after emergence on nectar sources. After its first blood meal the mosquito typically rests for 2-5 days for eggs to develop in the ovaries (gestation period). Eggs typically hatch within 48 hours (1-2 days). Larvae go through four instars and typically require 6+ days to reach the pupal form. Under ideal conditions, the pupa stage lasts 2 days. The duration of the egg, larvae and pupae stages depends on temperature and the mosquito species itself. For instance, Culex tarsalis might go through its life cycle in 14 days at 70 F and take only 10 days at 80 F. Also, some species have naturally adapted to go through their entire life cycle in as little as four days or as long as one month.
Photos: Institute for Clinical Pathology and Medical Research, University of Sydney, Australia
Culex Eggs
Aedes eggs
US Armed Forces Pest Management Board
Ovitrap with eggs of Aedes aegypti
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The pictures show an Aedes oviposition trap consisting of a black cup with tongue depressor wrapped in paper towel. Ae. aegypti and Ae. albopictus lay their eggs on moist surfaces next to shiny water sources like this. Stink water is not needed in Ae. traps, rather the mosquitoes are attracted to the black “hole” and reflections from the water.
Marin/Sonoma Mosquito and Vector Control District
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Mosquito emerging from pupal skin, a process that takes 10-15 minutes. After this the mosquito is no longer aquatic, but a flying insect. The adult life span is variable but may last 4-30 days.
Mosquito larvae Aquatic insects 4-14+ days from egg to adult Adults may be strong to
weak fliers, depending on species
Photo: M. Merchant, Texas A&M AgriLife
Mosquito mouthparts
Modified from Scientific American, Tom Prentiss
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Mosquitoes have piercing sucking mouthparts. The purple part is the hollow hypopharyx, through which saliva (and if the mosquito is infected, virus particles) flows into the wound. The saliva is the carrying agent for viral pathogens. A mosquito’s ability to catch, replicate and become infective is called vector competence.
Mosquito hosts Plant nectar or
honeydew for first 3-5 days after emergence Blood of vertebrate
hosts need for most species to initiate egg development Birds Mammals Reptiles Amphibians
Mosquito feeding
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Different species generally specialise in a particular kind of host, though some mosquitos, like the southern house mosquito, may feed on a variety of hosts, like birds and humans.
Floodwater species Psorophora columbiae Aedes vexans Standing water species Aedes albopictus/aegypti Aedes solicitans Culex quinquefasciatus Culex tarsalis
Floodwater species Psorophora spp. Aedes vexans
Typically live 4-5 days (up to one month) Excellent fliers (5-10 miles or more) eggs survive up to 2 years in soil painful bites
Floodwater species Difficult to control drainage of marshes floodwater control community fogging avoidance
Water only needs to stand 3-4 days to successfully breed mosquitoes Not important disease
vectors
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The most important thing to remember about floodwater mosquito species is that they are nuisances, but generally not important disease vectors—at least in most parts of Texas.
Major standing water species Culex, Aedes
Culex quinquefasciatus Culex tarsalis (West TX)
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Our most medically important species
Dept. Entomology, Texas A&M University
Culex spp. mosquitoes responsible for WNV human incidence
Sugumaran et al. 2009
Culex pipiens Culex tarsalis
Cx. quinquefasciatus
Courtesy G. Hamer, Dept. Entomology, Texas A&M University
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There are three important vectors of West Nile virus in the US. This map shows their approximate geographical distribution. Note that higher numbers of cases of WNV are seen in rural counties where Culex tarsalis is the key vector. Cu. tarsalis is more agricultural compared to the pipiens/quinquefasciatus complex.
Culex quinquefasciatus Southern house mosquito
delicate, dull brown mosquito; lacks bands on tarsi and proboscis prefers polluted water in
containers or other standing water mostly feeds on birds, but
thought to be principal vector of WNV to humans
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Our principal WNV vector in Texas.
Other standing water species Aedes albopictus* - Asian tiger
mosquito Since early 1990s in eastern Texas Daytime biter
Aedes aegypti – yellow fever mosquito container breeder vector of yellow fever, dengue fever being replaced by tiger mosquito?
Aedes solicitans – salt water mosquito saline/brackish water vicious, daytime biter
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Ae. solicitans is more common along Gulf coast areas in Texas.
Aedes albopictus Asian tiger mosquito
Most common mosquito complaints in Dallas, TX
Aedes albopictus Readily bites humans Breeding sites within 1-3 blocks 25% complaints can be traced to complainer’s property (Dallas Co. Health & Human Svcs. Dept.)
Why the difference between Aedes & Culex?
Culex resting sites 8 – 10 feet
Aedes
Culex
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As we will see, behavioral differences between Culex and Aedes affect treatment choices. Which species do you think would be better suited to control via air, versus ground spraying?
