Marching Behaviour in Migratory Locusts (Locusta migratoria) By: Christopher Payette and Tammer Masoud Research Project Proposal BIO318Y University 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: GregariousSolitarious

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 instarFifth instarAdult

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

Variables Independent variable: 1.Hunger of locust in rear position Fed up to trial, or starved for 24 hours before trial Dependent variable: 1.Number of bites exhibited by rear locust on followed locust 2.Average velocity travelled by followed locust Controls: 1.Hungry locust in front 2.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