Other External Secretions

Allomones are compounds produced by insects and their relatives that elicit antagonistic reactions between individuals (Bell and Carde 1984). They benefit the sender only, usually protecting it by warding off an attack by the receiver (Blum 1981). The pain-giving (not prey-seducing) venoms of female aculeate Hymenoptera, repugnant odors of many true bugs and beetles, and emetic body chemicals (cardiac glycocides and the like) in a few butterflies are of this category. Such also is the function of can-tharidin (Young 1984a, 19846), a terpenoid produced by "blister beetles" (Meloidae). When provoked, these beetles exude blood containing this substance from the tibio-tarsal articulations, and they are strongly avoided by insectivorous vertebrates and carnivorous insects.

Other secretions are external but cause no interactive response in other or the same species. These are utilitarian substances involved in the life processes of the producer. Examples are silk (Denny 1980) for cocoons and webs, adhesives to bind eggs in place, and materials such as wax or gums for building structures. Venom used by spiders, centipedes, scorpions, and others to obtain food also belong in this category. Regardless of function, arthropod venoms are usually compared from chemical or pharmacological standpoints (Bettini 1978).

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