Brief Summary

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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Comprehensive Description


 Integument strongly sclerotized, light tan to nearly black in color; setose, with hair-like setae throughout and spinose setae on legs and abdominal tergite IX. Thoracic and abdominal segments subcylindrical, surface coriaceous (Figs 2A–D, 3A–D, 4A–C, 5A–C, 6A–C).  Head. Prognathous or slightly declined (Fig. 7A–C), weakly dorsoventrally flattened, strongly constricted before occipital foramen. Epicranial stem one-fourth to one third head capsule length; frontal arms U-shaped or sinuate, occasionally obscured by sculpturing. Frons and dorsal portion of epicranial plates weakly to moderately rugose; punctate, punctures minute, lacking setae. Ventrolateral portions of epicranial plates setose; setae golden, erect; two stemmata present on each plate, pigmented spots often faded. Clypeus trapezoidal, often weakly transversely raised medially. Labrum with two transverse rows of six to fourteen erect setae present medially and subapically; anterior margin straight or weakly emarginate. Epipharynx (Figs 8, 9A–D, 10A–D) with stout spiniform setae along anterior margin, an anterior cluster of four to six variably arranged spinules, a subanterior transverse row of four small spinules subtended by two spinose setae and posterior cluster of six to eight small spinules; tormae symmetrical or asymmetrical. Mandible apex bidentate, mola concave. Ligula small, setation variable (Fig. 11A–C). Hypopharyngeal sclerome pentagonal or trapezoidal (Fig. 12A–B). Gula distinct, trapezoidal, widest in basal half. Antenna three segmented, cylindrical.  Thorax. Prothoracic tergum 1.2× or more length of meso- or metaterga (Figs 2A–D, 3A–D); anterior transverse striated band present, generally darker than protergal disc; lateral margins with granulated band either distinct or barely visible (Fig. 7A–C). Posterior transverse striated band present on all thoracic tergites. Meso- and metathoracic tergites wider than long. Mesothoracic spiracle simple, ovate, approximately 1.5× size of abdominal spiracles; reduced metathoracic spiracle visible, less than one-fourth size of mesothoracic spiracle. Legs. Prothoracic leg slightly longer, much thicker than meso- and metathoracic legs; prothoracic tarsungulus strongly sclerotized, sickle-shaped; dorsal surface of prothoracic femur with faintly indicated basal sclerotized band; dorsal surface of prothoracic tibia slightly more sclerotized than ventral surface.  Abdomen. Abdominal tergites and sternites I–VIII with transverse striated bands present along posterior margins. Abdominal sternite I setose (Fig. 13A–B). Abdominal segment IX (pygidium) triangular in dorsal view, gradually reflexed to apex, urogomphi absent, apical tooth present or absent (Fig. 14A–B); marginal row of socketed spines present around posterior two-thirds to one half of segment. Abdominal segment X located ventrally; pygopods short, subconical, each with erect setae.
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Pinacate beetle

The pinacate beetle, also known as the stink beetle, is a genus of darkling beetle endemic to the Sonoran Desert and adjacent regions of the U.S. Southwest and Mexico, usually the species Eleodes obscurus. The name is also loosely applied to a number of closely related species of Eleodes, of Western Mexico and the Western United States (including but not limited to the Great Basin), which, aside from the wooly darkling beetle, are not easily distinguished from each other. The name pinacate is Mexican Spanish, derived from the Nahuatl (Aztec) name for the insect, pinacatl, which translates as "black beetle".

The pinacate beetle is noted for its defensive tactic of standing on its head and squirting a noxious spray. This has earned it the additional names of clown bug and stink bug, names also applied to other unrelated insects.

References in popular culture[edit]

The pinacate beetle can be seen in the Sergio Leone classic western movie For a Few Dollars More, starring Clint Eastwood, Lee Van Cleef, and Gian Maria Volontè. In the scene just before the climactic final shootout between Colonel Douglas Mortimer (Van Cleef) and Indio (Volantè), Indio, while seated at a wooden table, being held at gunpoint by one of his gang members, smashes a pinacate beetle that scampers across the table in front of him.

In another Clint Eastwood movie, The Outlaw Josey Wales, Eastwood's character (Josey Wales) has a habit of spitting tobacco juice on several objects throughout the movie, including a hound dog's head, a dead assassin's forehead, and a pinacate beetle.

Off-road motorcycle riders, when discussing a particular machine, may refer to "stinkbug" handling when the machine has a front-low, rear-high feel to it, alluding to the pinacate beetle's defensive posture.

See also[edit]


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