How do flies keep clean? Head grooming in Drosophila

Abstract

Insect grooming prevents disease and preserves sensory functioning. Grooming movements have not been examined in flies, so this descriptive study was undertaken, using frame by frame analysis of videographs. Drosophila was chosen because of recent interest in neural systems that control grooming. Head grooming occurs in discrete bouts during which the well-bristled forelegs serve as brushes that sweep across areas of the head, usually several times per bout ($$\overline{X} \pm s=$$ 4.3 ± 1.1). Grooming is nearly always performed simultaneously by both legs. Sweeps across the head comprise cycles with a mean period of 95 ms and a modest amount of individual variation (CV = 9%); the sexes and species are virtually identical. In contrast to the precision of timing, head grooming is spatially irregular; no specific organ except the proboscis is groomed by itself; multiple areas are frequently groomed in a single bout and the two legs usually groom different areas of the head. Head movements comprise: (1) frequent, brief yawing motions, (2) pitching motions, and (3) occasional large rolls that enhance a foreleg’s access to the top of the head. The amount of time spent for head grooming depended on the number of sweep cycles (r = 0.99).