Insects Sense Weather, Adjust Mating Behavior, Study Says
When it comes to mating, insects feel the pressure — the atmospheric pressure.
According to a new study led by Jeremy McNeil, a biologist at the University of Western Ontario, insects adjust their mating behaviors to sensed changes in the weather. Dropping atmopsheric pressure generally indicates a storm, while rising pressure signals clear, sunny days.
“We have weather forecasts or you look at your phone and it tells you if you should take a raincoat or whether this is a good day to play golf,” McNeil told Weather.com. “This is sort of risk assessment on an insect’s part.”
McNeil and his team examined three different and unrelated insects in a lab: the cucurbit beetle (Diabrotica speciosa), the true armyworm moth (Pseudaletia unipuncta) and the potato aphid (Macrosiphum euphorbiae). In nature, when the females are ready to mate, they remain stationary and give off a sex pheromone that is carried on the wind. Males follow the scent to locate the female and attempt to mate. Using a bathymetric wind tunnel, Field and his team changed the atmospheric pressure and observed both the female “calling” behavior — excreting the sex pheromone — and the interaction between males and females in close proximity.
They found that in all three species, dropping atmospheric pressure caused decreased encounters. In the beetles, the males did not respond as well to the female odor, and the pair skipped normal pre-mating behavior, in which the male courts the female and the female decides whether she will accept the male.
In both rising or dropping pressure, the female aphids were less likely to exhibit their calling behavior, and less mating than expected occurred when the males and females were placed near each other. Moths had a similar reaction, though rising atmospheric pressure did not affect the female calling behavior.
According to McNeil, the results show that the insects respond to anticipated changes in the weather to prevent injury or death. Consider the tiny potato aphid female, wingless and about a tenth of an inch long, who, when searching for a mate, grips a leaf near a pond with her front four legs and sticks the other two into the air to emit her pheromone. In either dropping or rising pressure, the little aphid is in danger of being wrenched from her perch and flung about on stormy winds or rising thermal bubbles.
“With the exception of one animal, which is us, homo sapiens, the goal in life is to live long enough to reproduce,” McNeil said. “One of the questions we’re asking is, have they evolved the ability to assess short-term changes that may increase or decrease life expectancy, and do the changes that we see make any sense within the context?”
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