Cotalpa lanigera
goldsmith beetle

Goldsmith beetles, Cotalpa lanigera, are found in the eastern, central, and southwestern United States as well as southeastern Canada. (Coin, 2005)

Goldsmith beetles inhabit deciduous forests, woodlands, and fields near those woodlands. (Coin, 2005)

Goldsmith beetles are yellow or green in color and have a gold, metallic tint. Their elytra has irregular rows of small holes, but they do not have elytral markings. Goldsmith beetles are egg-shaped and are relatively heavy and large, ranging from 20 to 26 mm in length. Their ventral side is covered with dense, whitish wool-like hairs. (Coin, 2005; Lockwood, 1868; Coin, 2005; Lockwood, 1868)

Like most beetles, goldsmith beetles are endopterygotes that completely metamorphose. Once eggs hatch, larvae burrow to reach a food source and tend to feed voraciously; the larval stage is the principal feeding stage of the life cycle of goldsmith beetles. Larvae, which are whitish and C-shaped, are called grubs and are have limited motion. After 1 or 2 years, larvae pupate, and a fully formed beetle emerges from a pupa. (Libich, 2000; Williams, 2006)

Specific mating systems have not been identified in goldsmith beetles. In most beetles, the sense of smell is thought to play a considerable role in the finding of a mate. Pairing is generally short but in some cases can last for several hours. During sexual pairing, sperm cells are transferred to the female to fertilize eggs. (Libich, 2000)

Goldsmith beetles breed between April and July. After a gestation period of about 6 months, females lay their eggs in clumps on top of the soil below a tree. They lay a small number of eggs relative to similiar species. After a larval stage of 1 to 2 years, larvae enter a pupal stage. Adults emerge between May and July. (Breda, 2001; Coin, 2005; Lockwood, 1868; Williams, 2006)

Female goldsmith beetles lay their eggs on the soil below a tree near tree roots or rotting logs, potential food sources. Neither males nor females, however, are directly involved with parental care of their young after eggs are laid. (Coin, 2005; Libich, 2000; Williams, 2006)

The lifespan of goldsmith beetles is not well documented. However, development takes 1 to 2 years, and they often hibernate for 4 to 6 months. Based on developmental times, goldsmith beetles may live at least 16 to 30 months. (Breda, 2001; Coin, 2005; Lockwood, 1868)

Goldsmith beetles spend the first 1 to 2 years of their life underground as developing larvae. Larvae burrow through the soil surrounding the roots of trees, forming large round burrows that permit a great range of movement. When resting in burrows, they lie on the side of their body and curl up, protecting their delicate abdomens. Very young larvae are capable of limited movement that involves crawling on their ventral side. As larvae grow older and larger, they are able to move rapidly forward while lying on their dorsal side, legs facing upward, by making a serpentine motion. After pupation, they emerge from the soil as adults and begin an arboreal lifestyle, flying from tree to tree to feed. They are most active from twilight to dawn. During the day, they rest in the shade of leaves drawn together and held by their tarsi, forming an improvised tent. Adults are often seen at night flying around bright lights like those at gas stations. Adults usually hibernate during the winter, remaining about 38 cm below the soil surface. Larvae are usually found at greater depths. (Coin, 2005; Lockwood, 1868; McColloch, et al., 1928)

The home range of goldsmith beetles has not yet been determined. Adults have a greater potential range because of their flight capabilities. (Coin, 2005; Milne and Milne, 1980; Williams, 2006)

Members of the subfamily Rutelinae, including goldsmith beetles, use stridulating organs on their legs to communicate. Sounds are produced by a plectrum, a sharply confined ridge, moving across femoral pars stridens that have fine parallel ribs, much like a rasp. It is uncertain whether these sounds are produced as a component of mating behavior or if they have some other purpose. In several taxa, including the superfamily Scarabaeoidea, these stridulating structures may produce several different sounds that serve varying functions, such as courtship, aggression, and defense. (Wessel, 2006)

As larvae, goldsmith beetles feed on tree roots and rotting logs around which they burrow. Adults feed on willow (Salix), pear (Pyrus), hickory (Carya), oak (Quercus), and poplar (Populus) foliage. They generally feed at night. (Lockwood, 1868; Milne and Milne, 1980)

Goldsmith beetles are preyed upon by arboreal, insectivorous birds, including blue jays, yellow-billed cuckoo, and purple martins. Adult goldsmith beetles form tents by folding surrounding tree leaves around their bodies and holding them in place with their telsi. This provides shade as well as cover from predators. Their bright metallic color is also thought to be a form of warning coloration, though its effectiveness is unknown. (Judd, 1899; Lockwood, 1868)

Adult goldsmith beetles strip foliage from the trees in which they take up residence, most commonly willow (Salix) and poplars (Populus). They are also a source of food for many arboreal, insectivorous birds. Larvae help aerate the soil and play an important role in the decaying process of dead logs. Members of the subfamily Rutelinae, including goldsmith beetles, also act as hosts to sporeforming bacteria such as Clostridium as well as milky disease bacteria (Bacillus popilliae). (Coin, 2005; Klein and Jackson, 1992; Lockwood, 1868; Williams, 2006)

There are no known direct positive effects of goldsmith beetles on humans. Because they help aerate soil, break down rotting logs, and act as prey to a variety of birds, they help maintain a thriving ecosystem.

Because adult goldsmith beetles are quite effective at stripping foliage from trees, they are potential nuisances to some farmers and gardeners. However, members of this species tend to remain in forested areas.

Goldsmith beetles are often confused for far more destructive Japanese beetles, which are capable of causing a great amount of damage to soybean and corn crops. (Johnson, 1999)

Goldsmith beetles are usually considered uncommon, but have no special conservation status. (Coin, 2005)

Goldsmith beetles were featured in the short story "The Gold Bug" by Edgar Allan Poe. (Breda, 2001)