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Thylodrias contractus (Motschulsky, 1839)

Synonym(s) : 

Common names

  • Dermeste étroit
  • Odd beetle, Tissuepaper beetle
  • Speckkäfer

Classification:

  • Order:  Coleoptera
  • Family:  Dermestidae
  • Genus:  Thylodrias
  • Species:  contractus

Frequency index:

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Overview

The Thylodrias genus only comprises one species. These characteristic Dermestidae are atypical morphologically as well as biologically. Thylodrias contractus have a polyphagous and necrophagous feeding diet. They mostly dwell in large spaces (museums and warehouses) and are much less frequently found in individual houses. They are more particularly found in ethnographic and Natural History museums.

Recognition criteria

Adult

Size   

2 to 3 mm long (males) or 3 to 4.5 mm long (females).

Aspect    

Males are quite different from females, so that one could think they belong to 2 distinct species. Males are elongate, slightly sclerotized and they have soft elytra that frequently allow their abdomen to be seen. Their antennae and legs are quite developed and much longer than females’.
Females look like larvae: they have no elytra, no wings. They are longer and sturdier than males. Their antennae are relatively short, hardly longer than their head.
Whether male or female, the head is quite distinct from the pronotum, which is not always the case in other Dermestidae species.

Colour   

Males are yellowish to yellowish brown; females are a light reddish brown.

Larva

Size   

3 to 5 mm long

Aspect    

They look like small grubs with a carapace; they are entirely covered of stiff bristles that are quite visible.
They have a distinctive feature: they curl up in a ball, like woodlice, when they feel endangered.

Colour   

Old larvae are reddish to dark brown, young larvae are a much lighter colour

Development cycle

Little is known yet about the biology of that species.

The egg-laying period is 7 to 11 days long and larvae hatch about 1 month later. Larval development takes a long time.
It requires an average 275 days, but it can last up to 5 years in unfavourable (climatic and feeding) environments.

During their development, larvae undergo 5 to 12 consecutive molts. Once their growth is over, they remain nymphs for about 10 days before becoming adults. Imagoes live about 1 month.

Infected materials

Thylodrias contractus are inconspicuous insects that can particularly infest animal and insect collections. They can devastate collections by feeding on dead insects, or hairs and feathers of stuffed animals.

They also feed on wool and silk, and cause serious damage to fabrics and clothes.
In houses, where they are found more rarely, they rather feed on various debris.

Geographical distribution

The species is found in the whole northern hemisphere; it is fairly rare in Europe.