October 3, 2013
Insects Don’t Like To Do It In The Rain
Brett Smith for redOrbit.com - Your Universe Online
From a slight pain in the back to carefully observing the behavior of birds or cows, people have always been looking for signs of an impending storm. Now, a new study in the journal PLOS ONE has indicated the mating behaviors of various insects change in order avoid making themselves vulnerable during inclement weather.
The study researchers hypothesized some bugs exhibit a decrease in their mating habits to lower their exposure to life-threatening stormy weather. To explore this theory, the team of Canadian and Brazilian scientists examined the mating behaviors of three different species of insects under falling, stable, and increasing air pressure conditions.
Using an instrument called a Y-tube olfactometer to assess insect responsiveness toward odors, the group first exposed male curcurbit beetles to female pheromones and watched them under falling air pressure conditions. The male beetles exhibited less motion and interest in females than under stable or increasing air pressure. When these beetles were exposed to live female beetles under dropping atmospheric pressure, they put less effort into courtship. However, the physical act of mating took place faster in 63 percent of males, a phenomenon suggesting beetles’ sense of imminent death, the research team said.
According to study author José Maurício Simões Bento from the University of São Paulo, loss of interest in mating before a storm is an adaptation that "reduces the probability of injury and death of insects, which makes sense if you consider that high winds and rainstorms are life-threatening for them."
In the next part of the study, researchers examined how female armyworm moths and potato aphids altered their mating call behaviors under different atmospheric condition. While the female armyworms called less during decreasing air pressure, potato aphid females’ behavior was affected by both rising and falling atmospheric pressure.
“However, this is not particularly surprising when one considers that sexually mature potato aphid (females) move to the edge of the leaf and raise their metathoracic legs off the plant, as the pheromone is released from the hind tibia,” the researchers explained in their report. “In such a position, the small, wingless (females) only have four of their six legs grasping the plant and thus would be exposed to turbulent winds whenever there were changing atmospheric conditions. Consequently, they would have a high probability of being dislodged, resulting in a low probability of relocating a suitable overwintering host plant, and an increased incidence of mortality.”
Based on their analysis, the research team concluded all insects have likely adapted to respond to the potential for bad weather.
"The results presented show that three very different insect species all modify aspects of their sexual behavior in response to changing barometric pressure,” Bento said. “However, there is a great deal of interspecific variability in their responses that can be related to differences in size, flight ability and the (24-hour) periodicity of mating."
The researchers went on to say this behavioral change could have a knock-on effect on ecological communities. The team said they are now planning to look at the physical mechanisms associated with sensing pressure changes and this adaptive behavior.