Brief Summary Eleodes
Eleodes is not only the largest genus in terms of physical size in the Tenebrionidae, the darkling beetles, but it is also the largest in terms of the number of species. There are over 230 described species of Eleodes, about 132 of which are found exclusively in the Western portion of the US in arid and semiarid environments (Bernett, 2008). The larva of this genus is often referred to as a ‘false wireworm’ because they look similar to the larva of the family Elateridae, the true ‘wireworms’ (Bernett, 2008). In semiarid environments they are of economic importance because they feed underground on many plants. Although the larva can help irrigate the soil (Arnett, 2002) they can also be harmful to some plants that are commercially grown, such as wheat (Bernett, 2008). Adult Eleodes are especially noted for the odd posture they take while avoiding potential dangers: they point their abdomens in the air at about a 45° angle as they run away, almost as though standing on their heads. Running in this fashion may not be quite as speedy, but it does enable the beetle to utilize another defense. This genus is noted for the noxious quinone spray that some species produce when disturbed (Triplehorn, 2005). The abdomen-pointing behavior enables the Eleodes beetle to spray the chemical at potential predators. However, some mice have evolved a strategy to avoid this defense. By grabbing the beetle and sticking it into the dirt abdomen first, the mouse is able to begin eating the palatable portion of the beetle while the quinone is discharged without discomfort (O’Toole, 1986). Skunks have also developed a method for preying upon Eleodes: after capturing a beetle they roll it on the ground releasing the quinone onto the substrate and thus making the beetle edible. (Slodobochikoff, 1978). In addition to mammalian predators, fifty-one species of birds have also been recorded to feed on a particular species, E. tricostata. It is interesting to note that although this species of Eleodes does preform the abdomen-pointing behavior, it does not actually produce chemical defenses (McAtee, 1932).
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- O’Toole C. ed. 1986. The Encyclopedia of Insects. New York, NY: Facts on File, Inc.
- Slobodchikoff C.N. 1978. Experimental studies of Tenebrionid beetle predation by skunks. Behaviour. 66, 313-322
- Triplehorn, C.A., Johnson N.F. 2005. Borror and Delong’s Introduction to the Study of Insects: 7th edition. Belmont, CA: Thomas Learning.