Summary
Seventeen of the 24 species of Nearctic Arctiidae which we examined produced sounds under a variety of tactile and acoustic stimuli. Seven of 14 sound-producing species tested emitted their sounds in response to the hunting cries of insectivorous bats or simulations thereof. The sounds were generated by the buckling action of the microtymbal band (=striated band) on the surface of the modified thoracic metepisternum (=tymbal). Sound production is not dependent on the presence of microtymbals as four species of Callarctia possessed nonstriated, functional tymbals. In contrast, other species possessed striated, apparently nonfunctional tymbals.The sounds of the arctiids we studied were predominantly ultrasonic (> 20 kHz) and relatively faint (< 85 dB at 2 cm) compared with other insect sounds.The acoustic parameters of the arctiids surveyed revealed extremely high levels of variability in the sounds. Smaller species generally emit higher pulse repetition rates and more intense signals than larger ones. The behavioural contexts in which the sounds are produced and their relation to arctiid defense are discussed.
Methodology
The field research was conducted between May and September 1975 and 1976 at the Queen's University Biology Station near Chaffey's Locks, Leeds County, Ontario, Canada. Moths were collected throughout both summers from ultraviolet lights located around the station, identified, and immediately recorded. Scanning electron micrographs were made of the tymbals by Mr. L. E. C. Ling using techniques modified from Howden and Ling (1973).