Climate Change May Impact Gender of Insects that Help Farmers

There may some further impacts of rising temperatures when it comes to insects. Whether an insect will have a male or female offspring largely depends on the weather. The findings could mean that insect populations could experience a "hit" if climate changes continue.

"We know that climate affects the reproductive behavior of insects," said Joffrey Moiroux, one of the researchers, in a news release. "But we never clearly demonstrated the effects of climate change on sex allocation in parasitoids."

In this case, the scientists took a look at a species of oophagous parasitoid called Trichogramma euproctidis. This insect lays its eggs inside a host insect that is then internally consumed by the future larvae.

Like with bees, wasps and ants, the gender determination of Trichogramma parasitoids is called "hapladiploid." In other words, fertilized eggs produce female offspring while unfertilized eggs produce male offspring. It's also possible to predict whether the parasitoid will lay a son or daughter by examining the presence or absence of a pause in its abdominal contractions at the time of spawning; a pause means the egg will be fertilized.

In order to see if temperature could modify this behavior, the researchers exposed female Trichogramma to three different temperatures and then examined how their behavior was altered. They found that when it was hot, the females produced more males than at medium temperatures. In fact, the number of males produced increased by 80 percent. Surprisingly, though, they found the same was true at cold temperatures.

"There was a physiological stress that was not related to the females' choice," said Moiroux in a news release. "They intended to spawn as many females as during medium temperature, but the eggs were not fertilized after all. There were therefore more males produced at low temperature."

The findings reveal that these insects are drastically impacted by temperature. This could be a huge problem in the future. The parasitoid Trichogramma is actually an ally for farmers since its larvae kill insect hosts. It is, therefore, a largely beneficial insect.

"Predators and parasitoids are more sensitive to climate change, and this is why many researchers expect an increase in episodes of phonological asynchrony," said Moiroux in a news release. "This could be very harmful to crops if hosts escape the control of their natural enemies."

The findings are published in the journal Animal Behavior.