Two-winged insects such as houseflies and mosquitoes that are active during the light of day rely on their vision for flight control, but they also get help from organs called halteres, which grow where a second set of wings might otherwise be found and aid in navigation.
Scientists have wondered how four-winged insects most active at low-light times of the day, such as moths, accomplish complex navigational maneuvers, since they lack halteres. A research team studying hawk moths, the species Manduca sexta, has found an answer, with the unlikely help of microsurgery and Super Glue.
A tiny structure called the Johnston's organ, just above the moth's head at the base of the antenna, contains mechanosensors that allow the organ to function like a gyroscope, sensing a tug on the antenna and sending signals to the brain if the insect gets turned around by, for instance, a gust of wind, said Sanjay Sane, a University of Washington postdoctoral researcher in biology. He is the lead author of a paper describing the research in the Feb. 9 edition of Science.
"Whenever a creature is moving about, it has to have sensory information to tell it what it has done," Sane said. "If a person unintentionally turns around, the inner ear system or eyes will provide that information and allow for a course correction. Flying creatures need to know that information too, and when the light is low and the visual cues are hard to see they have to depend more on the mechanosensory system."
Hawk moths are among crepuscular insects, which are most active during low-light times of the day, at twilight or just before dawn. Like other insects, their antennae allow them to smell. But the researchers suspected the antennae also provided moths with the means to stay on the proper heading while in flight.
To test the theory, Sane removed the long part of the antennae, called flagella, just above the Johnston's organ, then observed as the insect
Contact: Vince Stricherz
University of Washington