Altner, H., and R. Loftus. 1985. Ultrastruc-ture and function of insect thermo- and hygroreceptors. Ann. Rev. Entomol. 30: 273— 295.

Dethier, V. G. 1963. The physiology of insect senses. Methuen, London. McIver, S. B. 1975. Structure of cuticular mechanoreceptors of arthropods. Ann. Rev. Entomol. 20: 381-397. Michelsf.n, A. 1979. Insect ears as mechanical systems. Amer. Sci. 67: 696-706. Slifer, E. H. 1970. The structure of arthropod chemoreceptors. Ann. Rev. Entomol. 15: 121-142.

Sound Production

Correlated with hearing in many insects and a few arachnids is sound production, another means of communication (Haskell 1961). There are a great variety of mechanisms for making sounds that are audible to other insects and to the human ear. Some, such as those resulting from the vibration of wings in flight, may be adventitious and apparently have no value to the animal, but most have a specific function and originate from unique, sometimes elaborate struc tures. Extraspecific uses usually are to startle and are protective (Masters 1979); intra-specific functions include the calling and courtship stimulations between the sexes, aggregation, spreading alarm, and giving the location of other colony members in social and semisocial forms.

Sounds may be produced as a byproduct of some activity such as feeding or wing movement, tapping the substrate, and ejections of air, but the major and most effective means of sonification involve fric-tional mechanisms and vibrating membranes (tymbals). The former, called stridu-lation, involves two facing surfaces that are roughened and that, when moved against each other, produce a sound. Such are the narrow scraper and file in the base of the fore wings of crickets and katydids. Many other insects, beetles, lepidopterous larvae and pupae, and so on, have broad corrugated or ridged areas that when rubbed together, give a variety of grinding, hissing, squeaking, and clicking sounds.

Sounds produced by the vibration of a membrane driven by muscles are common in Homoptera, Heteroptera, and some moths but are best developed in male cicadas. This sound-producing organ is located in the dorsolateral part of the first abdominal segment. Sound is made when the tymbal muscle contracts, pulling it back rapidly. Release allows it to return to the starting position suddenly against the air, and the resulting vibrations set up high-intensity air waves that may sound to the human ear like a deafening screech or harsh scream.

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