TAMPA, Fla. (WFLA) — It’s hard to find a person who doesn’t hate cockroaches. Whether it’s fear, disgust, or a combination, Americans hate the creepy crawly species. A study in SWNS reported roaches are the most hated bug in the United States.
Now, a study released by North Carolina State University shows our pesticidal habits may be changing how cockroaches breed, literally changing which males female roaches interact with, but not necessarily hurting reproductive chances.
Dr. Ayako Wada-Katsumata, principal research scholar at NC State, has studied insects for years and co-authored the study on cockroach mating habits. Wada-Katsumata found that the types of pesticides used to kill roaches have worked, but may have led to some bitter consequences for the bugs’ biggest haters.
According to the NC State study, it all comes down to taste.
“Gustatory receptor neurons (GRNs) in the mouthparts of the cockroach detect sugars, such as glucose, maltose and maltotriose, and mediate both foraging and sexual communication. During courtship, males expose specialized tergal glands and offer females an oligosaccharide-rich secretion that includes maltose and maltotriose, as well as phospholipids, cholesterol and various amino acids,” the study reads. “By attracting the female to his highly palatable secretion, the male places the female in the proper position for copulation and lowers her behavioral threshold to mate, thus gaining competitive advantage in female mate choice.”
In layman’s terms, most cockroaches like sweet things. During the roach mating process, males release a sweet smelling substance that attracts the female. When the female engages with the male, they attempt to eat the substance, allowing the male time to mate.
However, the study found that due to the use of pesticides killing females that prefer sweeter “nuptial offerings,” some female that are “averse to the simple sugar glucose get an unpleasant surprise when they mix their saliva with the male secretions,” causing them to “scurry away” before mating can complete.
“We’re seeing glucose-averse female German cockroaches turning down this nuptial gift – and the chance to mate – and wanted to understand more about the mechanism behind it,” Wada-Katsumata said. The researcher discovered this aversion among some roaches back in 2013. Her study at the time “informed bait manufacturers not to use glucose in baits.”
A follow-up study in 2021 “expanded this recommendation to all sugars that contain glucose.” Wada-Katsumata’s study said that “as more cockroaches with glucose aversion survive, that trait will be passed down in greater numbers.”
With the latest research released in May, Wada-Katsumata’s co-author said the use of pesticides containing glucose, sugar, was causing the glucose averse variants to become more “pronounced.”
“Cockroach saliva has a class of chemicals that breaks down sugars,” Coby Schal, Blanton J. Whitmire Distinguished Professor of Entomology at NC State said. “As females feed on their gift, maltose is rapidly converted to glucose, and glucose-averse females sense a bitter taste and stop feeding, which also ends the mating opportunity.”
It could also be shortening mating times, resulting in fewer successful breeding attempts.
“In short, the glucose aversion trait evolved under natural selection, but under sexual selection it is causing the male to modify his sexual secretion and behavior,” Wada-Katsumata said. A short abstract of the study says “the trade-off between natural and sexual selection under human-imposed selection can lead to directional selection on courtship behavior that favors the GA genotype.”
Use of sweet-tasting pesticides may be breeding the taste for sugar out of roaches, leading to a higher population size of glucose-averse critters, according to the study. While Wada-Katsumata said the long-term effects are not yet known, the previous studies warning against use of glucose in pesticides may mean current roach poisons will be less effective in the future.