Marching Behaviour inMigratory Locusts

(Locusta migratoria)

By: Christopher Payette and Tammer MasoudResearch Project Proposal

BIO318YUniversity of Toronto at Mississauga

Introduction to Locusts• Swarming behaviour in locusts can be destructive to

agriculture

• Most behavioural research on insects that swarm have the ultimate goal of preventing the formation of plagues

• Questioning the motive in the migration of swarms lead to behaviour analysis of the Mormon cricket

• Mormon crickets, like locusts, are deprived of limiting nutrients (proteins and salts) that can be found in their exoskeleton, and as a result can exhibit cannibalism in the context of swarms

• Thus, the swarm does not only migrate in the pursuit of food, but also partly due to the threat of being bitten by following locusts

Introduction Continued• Stephen J. Simpson along with Iain Couzin investigated

the motivation in the driving of a swarm in Desert locusts

• Most discoveries concerning these behaviours have been found in the most commonly studied Desert locust, Schistocerca gregaria

• Little is known on such behavioural aspects in the swarms of migratory locusts making it an ideal research topic

Migratory Locusts• There are two phenotypes, which differ in

behaviour, physiology, and morphology

• Polyphenisms occur due to mainly the rearing environment

• Two phenotypes:Gregarious Solitarious

Migratory Locusts• Locust nymphs undergo development in five stages,

called instars, and have no larval stage

• Each nymph sheds its cuticle in transition to the next instar stage

• All instars don’t have wings as they are under development; thus, forcing nymphs to march in swarms

• In our experiment, marching behaviour will be studied in fifth instar nymphs, which will be related to natural occurrences in swarms

First instar

Fifth instar Adult

Research Question:“ Is there a motivational factor in marching behaviour

associated with the prevention of cannibalism in Locusta migratoria?”

Hypothesis:“The velocity of the marching exhibited by the locust

being followed will be affected by the presence of a locust behind it.”

Null Hypothesis:“The velocity of the marching exhibited by the locust

being followed will not be affected by the presence of a locust behind it.”

Prediction:“As hunger increases in the following locust, its

tendency to exhibit cannibalistic behaviour will increase. In turn, when more bites on the abdomen of the leading locust occur, the velocity travelled by that locust will increase.”

Behaviour we’ll be observing

• Marching behaviour: Coordinated movements of individuals in a group walking with a purpose. • In experiment, marching behaviour will be

observed in a circular apparatus with two locusts forced to be one behind the other.

• Cannibalistic behaviour: Consuming an individual of the same species as a food source.• In experiment, cannibalistic behaviour will be

defined by the number of bites on the abdomen of the locust in front of it.

Observations/Apparatus• Circular apparatus made of plastic tubing

• Diameter only wide enough for one locust to march through at a time. i.e. no overtaking, jumping, or changing direction• Red lines = sliders to allow control of locusts’ movement & direction

• Ethanol washing will avoid pseudo replication

• Lap marker allow us to measure distance travelled

• Recorded time will allow us to calculate for locust’s velocity

• 30 fifth instar males for sample size; two specimen per trial

VariablesIndependent variable:1. Hunger of locust in rear position

• Fed up to trial, or starved for 24 hours before trial

Dependent variable:2. Number of bites exhibited by rear locust on

followed locust3. Average velocity travelled by followed locust

Controls:4. Hungry locust in front5. Velocity of hungry locust alone will be

measured to compare

Questions?

Statistics• Only two categories for the independent

variable:• Starved or fed

For average velocity:• Continuous variable• Use Student’s t-test if there is a normal

distribution• Use Mann-Whitney U test if distribution is not

normal

For number of bites exhibited by rear locust:• Categorical variable• Use Pearson’s χ² test