Landois offers the following summary of the kinds of noises produced by beetles:
1. Tapping sounds (Bostrycinæ, Anobium). 2. Grating sounds (Elateridæ).
Mutilla makes a rather sharp noise by rubbing one abdominal segment against another. Ants (Ponera) have a stridulating apparatus, and other genera numerous (20) ridges between the segments.
Even certain moths and butterflies emit a rasping or crackling noise. The death’s-head moth and other sphinges cause it by rubbing the palpi against the base of the proboscis. These and certain butterflies are provided with parallel ridges forming a rasp on the “basal spot” of the inner side of the basal joint of each palpus (Reuter). A South American butterfly (Ageronia feronia) can be heard for several yards as it flies with a crackling sound. Hampson finds that the cause of the clicking sound is due to a pair of strong chitinous hooks attached to the thorax, against which play the spatulate ends of a pair of hooks attached to the fore wings. An Australian moth (Hecatesia) flies with a whizzing sound; Vanessa is said to be sonorous.
The males of Orthoptera produce their shrill cries or chirping noises, 1, by rubbing the thighs against the sides of the body (Acrydiidæ); 2, by the friction of the base of the fore wings on each other (Locustidæ); 3, by rubbing the base of the upper on the base of the hinder or under pair (Gryllidæ), in the two last there being a shrilling apparatus consisting of a file on the hind wings, which rubs on a resonant surface on the fore wings. The females are not invariably dumb, both sexes of the European Ephippigera being able to faintly stridulate. Corixa also produces shrill chirping notes. (Carpenter.)
Certain insects also hum, and have what may perhaps be called a voice. The cockchafer, besides humming with the wings, produces a sound almost like a voice. In the large trachea, just behind each spiracle, is a chitinous process, which is thrown into vibrations by the air during respiration, and thus produces a humming noise. (Lubbock.) Such is also the case with flies, the mosquito, dragon-flies, and bees. In flies and dragon-flies the “voice” is caused by the air issuing from the thoracic spiracles; while in the humble-bee the abdominal spiracles are also musical. The sound made by the spiracles bears no relation to that caused by the wings. Landois tells us that the wing-tone of the honey-bee is A′; its voice, however, is an octave higher, and often goes to B″ and C″.
The sounds produced by the wings are constant in each species, except where, as in Bombus, there are individuals of different sizes; in these the larger ones generally give a higher note. Thus the comparatively small male of Bombus terrestris hums on A′, while the large female hums an entire octave higher.
From the note produced the rapidity of the vibrations can be calculated. For example, the house-fly, which produces the sound of F, vibrates its wings 21,120 times in a minute, or 335 times in a second; and the bee, which makes a sound of A′, as many as 26,400 times, or 440 times in a second. On the contrary, a tired bee hums on E′, and therefore, according to theory, vibrates its wings only 330 times in a second. Marey has confirmed these numbers graphically, and found by experiment that the fly actually makes 330 strokes in a second. (Lubbock.)
A different kind of musical apparatus is that of the cicada, which has been elaborately described by Graber. The shrill, piercing notes issue from a pair of organs on the under side of the base of the abdomen of the male, these acting somewhat as two kettle-drums, the membrane covering the depressions being rapidly vibrated.