Why Cockroaches Groom Themselves
Insects spend a lot of time grooming. In a study by North Carolina State University, researchers show that insect grooming; specifically antennal cleaning removes both environmental pollutants and chemicals produced by the insects themselves.
The findings show that grooming helps insects maintain acute olfactory senses that are responsible for a host of functions, including finding food, sensing danger and even locating a suitable mate. The findings could also explain why certain types of insecticides work more effectively than others.
North Carolina State entomologist Coby Schal and post-doctoral researchers Katalin Boroczky and Ayako Wada-Katsumata wanted to explore the functions of this behavior. They devised a simple set of experiments to figure out what sort of material insects were cleaning off their antennae, where this material was coming from, and the differences between how groomed and ungroomed antennae functioned.
The researchers compared cleaned antennae of American cockroaches with antennae that were experimentally prevented from being cleaned. They found that grooming cleaned microscopic pores on the antennae that serve as conduits through which chemicals travel to reach sensory receptors for olfaction. Cockroaches clean their antennae by using forelegs to place the antennae in their mouths; they then methodically clean every segment of the antenna from base to tip.
The researchers also tested groomed and ungroomed cockroaches antennae to gauge how well roaches picked up the scent of a known sex pheromone compound, as well as other odorants. Clean antennae responded to these signals much more readily than ungroomed antennae.
The researchers then put carpenter ants, houseflies and German cockroaches to many of the same tests. Although they groom a bit differently than cockroaches, flies and ants seem to rub their legs over their antennae to remove particulates, with ants then ingesting the material off their legs.
“The evidence is strong: Grooming is necessary to keep these foreign and native substances at a particular level,” Schal says. “Leaving antennae dirty essential blinds insects to their environment.” Schal adds that there could be pest-control implications to the findings. An insecticide mist or dust that settles on a cockroach’s antennae should be ingested by the roach rather quickly due to constant grooming. That method of insecticide delivery could be more effective than relying on residual insecticides to penetrate the thick cuticle.