— This article by Jerry Cates and John Willis, first published on 16 May 2012, was last revised on 14 July 2012. © Bugsinthenews Vol. 13:05(04).
On Thursday, 10 May 2012, at a large retirement community in Temple, Texas, I picked up two large beetles that had been saved for me by John Willis, the Director of Facilities. John, an experienced student of nature and the outdoors, takes care to preserve intact specimens of unusual organisms that are found at this facility, so they can be studied in the lab.
One of the beetles John collected here measured about 1.75 inches in length, and the other was slightly smaller. On the anterior dorsum of the body (specifically the pronotum, i.e., the dorsal surface of the prothorax, just behind the head) are two large black spots, having the superficial appearance of eyes, outlined with cream-colored scales. A second set of less sharply defined eye-spots are on the elytra, i.e., the beetle’s hardened, protective forewing that covers the membranous the hindwings underneath them.
These beetles are known in Texas as the Texas eyed click beetle (Alaus lusciosus); a very similar beetle, the common eyed click beetle (Alaus oculatus), is found in the same locales in Texas, but ranges eastward to Florida, and northward to S. Dakota and Quebec as well. The Texas eyed click beetle was first described in 1832 by the English entomologist Frederick William Hope (1797-1862); the common eyed click beetle (A. oculatus) was first described in 1758 by the Swedish taxonomist Carolus Linnaeus (1707-1778).
A member of the housekeeping staff at this retirement community had been bitten by one of the beetles. The bite had left an unbroken red welt, and the hapless victim wondered if the bite might put her at risk of infection or, worse, envenomation.
I assured John that the bite of this beetle, though mildly painful at the moment the bite occurs, is rarely capable of breaking human skin, though — as one comment to this post informs us — such injuries can occur especially with small children. As the animal is not venomous, such bites have not been know to result in conditions of a medical nature. Further, because these beetles are the adults of larval forms that prey on destructive wood and root boring insects of trees and shrubs, they are extremely beneficial members of the ecosystem and should be prized and appreciated, rather than feared.
The beetle’s outward appearance, however, is imposing, even frightening, to those encountering it in the wild. Not only does its enormous size (at least for a beetle) command respect, but the “eyes” on its back tend to startle those who spy it in their yards and homes (yes, they can wander inside, if given the opportunity).
Evidently that “startle response” is shared by most other animals, too, which most likely explains why the “eyes” of the eyed click beetle are there in the first place. Wickler (1968), for example, devotes several pages, in his text on mimicry in plants and animals, to the subject of eye-spots. He notes first that the attention of humans is immediately drawn to eye-spots when they are observed on an animal in its natural setting. It seems that the human psyche is instinctively programmed (my wording, not Wickler’s) to pay close attention to eyes or close approximations thereto. Yet, he points out, such spots were almost certainly not designed to influence humans, since they and these beetles rarely interact. Thus the spots may not be intended to resemble organs of sight. Only after scientific investigators conducted experiments, designed to ascertain how such spots are perceived by the beetle’s predators and mates, could it be determined if they confer a defensive or reproductive advantage upon the animal they adorn. Those experiments suggest that — with respect to beetles that are preyed on by birds — their predominant function is of a defensive nature.
Wickler notes that, among all the animal patterns observed in nature, the eye-spot constitutes a major grouping. Such spots are found, for example, in Peacock feathers, on certain butterflies and moths, as well as on a few caterpillars, fish, and turtles. In many cases the spots are in multiples that seem unlikely mimics of eyes, but in some, as with the eyed click beetle, they are in pairs that mimic eyes in a dramatic fashion. Birds that happen upon animals with such spots that would otherwise be quickly snatched up tend to hesitate before attacking, and often pass the eye-spotted insect up altogether.
- Kingdom Animalia — multicellular, eukaryotic organisms whose body plans become fixed during development, some of which undergo additional processes of metamorphosis later in their lives; most are motile, and thus exhibit spontaneous and independent movements; all animals are heterotrophs that feed by ingesting other organisms or their products.
- Phylum Arthropoda (Linnaeus, 1758) — invertebrate animals with external (exo) skeletons, segmented bodies, and jointed appendages; named using the two Greek words ἄρθρον (pron. árthron), meaning “joint” + ποδός (pron. podós), meaning “leg” = “jointed leg”; comprised of insects, arachnids, crustaceans, among others;
- Class Insecta (Linnaeus, 1758) — named using the Latin word insectum, a calque of the Greek word ἔντομον (pron. éntomon) = “(that which is) cut into sections”; comprised of arthropods with chitinous external (exo-) skeletons, a three part body composed of a distinct head, thorax, and abdomen, the midmost part having three pairs of jointed legs, and the foremost part having a pair of compound eyes and antennae;
- Order Coleoptera — beetles; named from the two Greek words κολεός (pron. koleos) meaning “sheath” + πτερόν, (pron. pteron) meaning “wing” = “sheathed wing”; most beetles exhibit two pairs of wings, the first pair, or “elytra,” forming a sheath over, and thus protecting, the rear pair of relatively fragile, membranous wings;
- Family Elateridae (Leach, 1815) — typical click beetles, as distinguished from beetles in the Cerophytidae and Eucnemidae families; also known as elaters, snap beetles, spring beetles, and skipjacks; characterized by the incorporation in their exoskeleton of a prosternal spine that — when inserted into a specialized mesosternal notch while the beetle’s back is arched, and thereupon pressing the spine ventrally against the sternum while slowly straightening the back until the the spine tip escapes from the notch — forcibly snaps the head dorsally; this produces an audible click and propels the beetle’s body in the direction defined by the snapped head; besides being used as an effective defense against predation, the procedure described also works to right a beetle that has rolled onto its back; over 9000 species of click beetles are recognized worldwide, more than 950 native to North America;
- Genus Alaus (Linnaeus, 1758) — the etymology of the generic name is obscure; a genus of click beetles comprised of some 5 recognized species;
- Species Alaus lusciosus (Hope, 1832) — the specific name is derived from the Latin word luscus, meaning one-eyed;
Anatomy: in process
Behavior and habitat: This is one of the largest of the click beetles and is found mainly in deciduous hardwood forests, though mainly around rotting logs. The larval stage is spent in the soil, in rotting or decayed wood, and in and around the rootstock of trees and woody herbs, as a long, slender, wormlike predator of other insects, primarily the larvae of root and wood borers. Adults emerge from early spring through early fall, and eat sparingly if at all, though some authorities suggest they may feed on the nectar and juices of plants during their life aboveground.
Physiology and Distinguishing Characteristics:
A. Larvae are yellowish to dark brown in color, up to 50mm long, slender, jointed (having the appearance of segmented worms), hard-shelled (thus are often called wire-worms), with dark heads and three pairs of legs; the four anterior segments are dark brown; the 9th segment (counting from the head backward) has what appear to be pronged teeth, while the 10th segment has two anal hooks, 10-12 spines, and seta.
B. Adults are from 24-45 mm (0.94-1.77 inches) in length, with a black or dark brown background coloration upon which is imposed a pattern consisting of pale white or yellowish-white scales; one to three sets of eye-spots are superimposed in the resulting pattern, one (the most pronounced of the three) on the anterior half of the dorsal pronotum, the second (sometimes indistinct or missing) on outside edge of the anterior half of each elytra, and the third (also sometimes indistinct or missing) on the outside edge of the posterior half of each elytra; the presumed effect of these eye-spots is to give the beetle the appearance of an animal with one to three sets of eyes, so that predators (chiefly birds) are confused about which end of the beetle to attack first; it is likely many birds will pass this beetle up altogether, in the mistaken fear it may be impossible to sneak upon it, or that it may be able to retaliate.
Similar Beetles: The blind click beetle (Alaus myops), so-called because all the eye-spots are missing or indistinct, is 25-38mm (1-1.5 in.) long, reddish brown to black, and found chiefly in the Southeast U.S.; the common eyed click beetle (Alaus oculatus) is 24-45mm (0.94-1.75 in.) long, with circular eye-spots and yellowish-white scales on its body, and is widespread in the eastern U.S., as far north as Quebec, westward to S. Dakota, and southward to Florida; the range of this species overlaps with that of the Texas eyed click beetle (Alaus lusciosus), but apparently neither of those species overlaps with the very similar Zuni or Arizona eyed click beetle (A. zunianus).
Distribution: The Texas eyed click beetle (Alaus lusciosus) is found in central, southern, and sections of eastern Texas; the common eyed click beetle (Alaus oculatus) is widespread throughout the eastern half of the United States, as far north as Quebec westward to South Dakota, and southward to Florida and south Texas; the two species can be distinguished by the fact that the white scales on their dorsal surfaces are more evenly distributed in a. oculatus, but coalesce into clumped sections in a. lusciosus.
- Arnett, R., et al. 2002. American Beetles, Volume II: Scarabaeoidea through Curculionoidea. CRC Press.
- Bugguide. Common eyed click beetle (Alaus oculatus). Department of Entomology, Iowa State University.
- Bugguide. Texas eyed click beetle (Alaus lusciosus). Department of Entomology, Iowa State University.
- Bugguide. Zuni eyed click beetle (Alaus zunianus). Department of Entomology, Iowa State University.
- Milne, L., and M. Milne. 1984. The Audubon Society Field Guide to North American Insects and Spiders. Alfred A. Knopf, New York
- Montiero, A., et al. 2006. Comparative insights into questions of lepidopteran wing pattern homology. Bio Med Central 6:52.
- Wickler, W. (Trans. by R. Martin). 1968. Mimicry in Plants and Animals. World University Library/McGraw-Hill Book Company.
- White, R. 1983. A Field Guide to the Beetles; the Peterson Field Guide Series. Houghton Mifflen Company.
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