Insects Groom to Improve their Sense of Smell

A new study finds that insects groom in order to improve their sense of smell.

Olfactory senses of the insects are responsible for a string of functions, including finding food, sensing danger and even locating a suitable mate. Researchers from North Carolina State University have found that insects groom, in particular clean their antennae, to remove environmental pollutants and chemicals produced by the insects themselves. This helps in improving their sense of smell.

The findings could also explain why certain types of insecticides work more effectively than others. For their study, the research team compared cleaned antennae of American cockroaches with antennae that were experimentally prevented from being cleaned. They wanted to figure out what material the insects were cleaning off their antennae, where this material was coming from, and the differences between how groomed and un-groomed antennae functioned.

Researchers found that the cockroaches cleaned the microscopic pores on the antennae through which chemicals travel to reach sensory receptors for olfaction. They placed their antennae in their mouths using the forelegs and then cleaned every segment of the antenna from base to tip.

Apart from volatile and non-volatile chemicals accumulated on the antennae, the researchers also discovered the accumulation of cuticular hydrocarbons - candlewax-like substances that regulate water loss in cockroaches.

"It is intuitive that insects remove foreign substances from their antennae, but it's not necessarily intuitive that they groom to remove their 'own' substances," Coby Schal, entomologist at North Carolina State University, said in a statement.

Researchers then compared the groomed and un-groomed antennae of the cockroaches in order to understand the effects of their grooming behavior. They found that un-groomed antennae accumulated four times the amount of cuticular hydrocarbons gathered by groomed antennae, according to BBC reports.

Unlike groomed antennae, the cockroaches with un-groomed antennae were less responsive in picking up the scent of sex pheromones and other odorants, the researchers said. 

They also identified other insects such as carpenter ants and houseflies that employ different methods to clean their antennae. "The evidence is strong: Grooming is necessary to keep these foreign and native substances at a particular level," Schal concluded. "Leaving antennae dirty essentially blinds insects to their environment."

The findings of the study are published online this week in Proceedings of the National Academy of Sciences.