Thylodrias contractus, also referred to as the odd beetle or tissue paper beetle, is one of the many beetles in the family Dermestidae, also known as the carpet beetles. It is called "odd" because of its sexual dimorphism. It can be a pest at times but rarely.

Identification

T. contractus is an elongate beetle with slender legs. Male beetles can be recognized by their yellowish-brown elytra and covering of silky, white hairs. The abdomen has seven sternal segments and the antennae are filamentous rather than club shaped, which distinguishes it from all other members of the carpet beetle family. The females of this species look very different from the males and actually resemble larvae and although they are free living and have legs and antennae, they do not have elytra or hind wings, like most adult Coleoptera. The larvae of the odd beetle resemble the larvae of most of the other members of the Dermestidae family. However they lack a tuft of hair at their posterior end as well as the long hairs along their dorsal surface, instead at the end of each segment of the body there is a row of short bristles.

Distribution

Widely spread in North America, odd beetles are an invasive species from Asia. Since the larviform females are wingless, it is believed that the odd beetles were introduced.

Life cycle

Like all beetles, the odd beetle undergoes complete metamorphosis, or a dramatic reorganization of the body plan of the insect and the formation of two distinct life stages, growth and reproduction, which are separated by a pupal phase. Although the female is larviform, she also undergoes metamorphosis from a true larva to a sexually mature adult. Once T. contractus has reached sexual maturity, the female produces a pheromone, which attracts the male beetles to her. Once the female has mated she no longer produces this pheromone, which suggests that female odd beetles mate only once. There is no indication that this is true for male beetles.

Behavior

Odd beetles are often incorrectly named tissue paper beetles for their mistaken behavior of eating tissue paper. Instead, odd beetles actually chew away tissue paper to feed on material wrapped in it, such as fabrics like wool and silk, or dried animal matter like fur, feathers, and skin. Some captive odd beetles are also known to feed on cooked beef liver.
They are usually found in dark corners of human dwellings, like those in drawers, cupboards, and even museum displays.
Odd beetles display peculiar behaviors when they are stressed. When they are disturbed, they tend to ball up. Sometimes, when the odd beetle is under stress, it undergoes retrogressive molting. Instead of growing larger, it grows smaller and smaller with each molt, until it becomes a miniature adult.

Human Impact

Odd beetles feed on dried animal matter, including skins, hides, fur, feathers, insect collections, and natural fiber fabrics such as silk and wool. They can also penetrate tissue paper used to wrap their food materials. For this reason the odd beetle is sometimes called the "tissue paper beetle".

External links

• Thylodrias contractus on UC Riverdale Entomology
• "Museum Pests"