How Males Support Females in Extreme Locust Heat

A team of entomologists at the Mauritanian National Desert Locust Center, under the Center National de Lutte Antiacridienne, has made an intriguing discovery: male locusts frequently mount females during the hottest part of the day while they are laying eggs.

Their research, published in the journal Ecology, involved conducting field studies and experiments to explore how male locusts help protect females from extreme heat. Previous studies have indicated that locust swarms can rapidly destroy vast areas of crops and that these insects breed quickly. Typically, females are known to lay eggs in the cooler evening hours, yet some have been seen doing so during the sweltering daytime.

The researchers sought to understand how females manage to lay eggs in such high temperatures. They undertook several trips into the Sahara during swarming periods and observed that males would mount females as they laid eggs, a behavior exclusive to daylight hours. This action is similar to what occurs at night, where it helps deter other males from interrupting the egg-laying process.

To verify that this behavior wasn’t coincidental, the team specifically studied pairs during intense heat, with temperatures soaring to 48°C. They found that about 90% of females were mounted by males during these hot conditions. Furthermore, the pairs adjusted their positions in relation to the sun, remaining aligned with its rays. Using thermal cameras, they revealed that mounted females had cooler body temperatures compared to those not being mounted.

In an additional experiment, the researchers secured dead locusts to sticks in pairs and individually to the ground. By monitoring the body temperatures, they found that the dead locusts provided effective shade, keeping those beneath them cooler.

The implications of this research could lead to innovative pesticide approaches to control locust infestations, potentially minimizing crop damage.