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Anjana Duwal, Carlton, Christopher E.
The largest click beetles in the U.S. are the eyed click beetles, with two species found in Louisiana. Adults in the family Elateridae possess a click mechanism comprising a blunt spine on the underside of the first thoracic segment (prothorax) that fits into a slot on the second segment (mesothorax). When the beetle flexes its thoracic muscles, tension on the slot suddenly releases the embedded spine, causing the beetle to propel its body into the air with an audible click, thus the common name, click beetles. Eyed click beetles are the largest members of the family in North America, ranging from 2.5 cm to 4.5 cm in body length. The adults are mainly black with bold, white speckles. A pair of large, black spots ringed with white on the top of the thorax (pronotum) are referred to as eyespots and presumably serve as a predator deterrence adaptation. The actual eyes are small and located in normal positions on the sides of the head. The eastern eyed click beetle, Alaus oculatus, is typically larger than the small eyed click beetle, A. myops, though both species are variable in length. The eyespots of A. oculatus are about one-third the length of the visible thorax, while those of A. myops are one-fourth the length of the thorax. Adults of the small eyed click beetle often have a brown or tan hue.
The larvae may reach 4 cm in length when fully developed. Larvae are softer-bodied than most other click beetle larvae, light to dark brown in color, with lighter areas on the sides of the body and between segments. They possess a U-shaped arrangement of stiff spines around the last body segment, including a pair of forked spines (urogomphi) that are longer than the adjacent spines.
Four additional species of eyed click beetles are known from the U.S. Notably, the range of the Texas click beetle, Alaus luctuosus, extends into eastern Texas. This species is similar to the eastern eyed click beetle, but its white markings are more extensive and grouped into clumps. A few online records of the Texas click beetle in Louisiana exist, but occurrence of the species in Louisiana requires confirmation based on collected specimens.
Adult eyed click beetles emerge during spring, flying during the daytime in search of mates and egg-laying substrates. Females lay eggs on the trunks of dead standing trees or in adjacent soil. Larvae live within dead wood and are opportunistic predators of other beetle larvae and soft-bodied insects. Larval duration is highly variable, from a few months to more than a year. Larvae reared in captivity undergo as many as 20 growth stages (instars) and require up to 22 months to fully mature. Pupation occurs in loose, dead wood or adjacent soil. The pupal stage requires up to a month during warm weather, or for the duration of the winter in the case of overwintering pupae. Adults feed on nectar or other plant exudates. Adults can be found under loose bark of dead trees and larvae are occasionally recovered from well-rotted, woody debris. The eastern eyed click beetle is mainly found in wood of deciduous trees. The small eyed click beetle is more common in pines.
Wood-dwelling click beetle larvae, such as eyed click beetles, are predatory or omnivorous and pose no threat to crops. However, larvae of a small number of soil-dwelling species may damage roots of crops and are referred to as wireworms. Eyed click beetles mainly prey on other wood-boring beetle larvae. In one study, a single captive larva of an eastern eyed click beetle consumed 200 long-horned beetle larvae. Other captive larvae have been reared on crushed crickets and small bits of mouse meat. Larvae are relatively common in dead wood in appropriate stages of decay and likely serve as important natural control agents of wood-feeding insects.
Alaus oculatus adult, New Orleans, Louisiana (John Carlson, iNaturalist, Creative Commons BY-NC 4.0).
Alaus myops adult, Caddo Parish, Louisiana (Royal Tyler, iNaturalist, Creative Commons BY-NC 4.0).
