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Anthrenus verbasci (Linnaeus, 1767)

Synonym(s) : 

Byrrhus verbasci Linnaeus, 1767, Bostrichus varius Fabricius, 1775, 
Anthrenus varius Fabricius, 1775 ,Anthrenus florilegus Fourcroy, 1785 
Dermestes varius Schneider, 1785, Anthrenus adspersus Herbst, 1797 
Anthrenus tricolor Herbst, 1797, Anthrenus pictus Germar, 1813 ,
Anthrenus tomentosus Thunberg, 1815

Common names

  • Anthrène bigarré des tapis ; Anthrène à bandes
  • Varied cabinet beetle ; Small cabinet beetle
  • Gorgojo de las alfombras
  • Wollkrautblütenkäfer

Classification:

  • Order:  Coleoptera
  • Family:  Dermestidae
  • Genus:  Anthrenus
  • Species:  verbasci

Frequency index:

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Overview

In summer, adult varied cabinet beetles visit flowers, more particularly Apiaceae (Umbellifera) flowers and mullein to feed on their nectar.
As soon as temperatures get cold, they seek shelter and sometimes leave natural environments to find warmer places.
That is why they often find refuge inside houses.
They also have a special liking for museums or similar premises, where their larvae can keep feeding and thereby severely damage insect collections and stuffed animals (animal hairs and bird feathers).

Anthrenus verbasci can sometimes be useful for they are auxiliaries (predators) of caterpillar larvae such as gipsy moths’ larvae. Eggs hatch mainly in autumn and the full development cycle can take up to one year. Anthrenus verbasci adults are hardly ever harmful. Only their larvae, whose development phase fully takes place inside clothes, furs, carpets, furniture upholstering and most of all in insect collections, cause huge damage.

Anthrenus verbasci are most harmful during the hottest months of the year, i.e. from June to October. When possible, populations can be partly limited by using a fitted vacuum-cleaner on materials infested by their larvae (carpets, clothes, woollen materials…).

Inspecting collections regularly can avoid wide-scale infestation. Few natural enemies of cabinet beetles are known, except Bethylidae Hymenoptera which infest their larvae, or the Pseudoscorpion Arachnid Cheiridium museorum (Leach) which is a predator of their larvae.

Anthrenus verbasci adults look very much like Anthrenus museorum or Anthrenus flavipes adults; nevertheless, the identification criteria given for each of those species in our fact-sheets make it possible to tell between them. Varied cabinet beetles are strongly attracted by light and can easily be trapped using ultra-violet light.

Recognition criteria

Adult

Size

2 to 3.5 mm long


Aspect    

Egg-like shape, quite round at the front and rear ends. Small head, and rather short, 11-articled antennae; the last 3 articles form a compact club.
Slightly round eyes (dented in Anthrenus flavipes) ; rather short legs that can fold back into their grooves on the ventral face.

Short pronotum, ending in a wide V-shape near the elytra.
Narrow elytra (1.4-fold more in length than in width), with parallel borders on ¾ of their length.
Elytron scales are narrow and filiform in A. verbasci whereas they are less elongate in A. museorum and round in A. flavipes.


Colour  

Ochre yellow to brown background colour, with whitish or black blotches or stripes. Elytra have 3 wave-shaped, horizontal whitish stripes. The underside of the abdomen is mostly ash-grey, with dark blotches at the lateral end of each sternite.

Larva

Size   

4.5 mm when fully developed.


Aspect    

Look like small white grubs whose body is fully covered in spiky hairs.
Narrow body at the front, getting gradually wider toward its rear end, unlike Anthrenus flavipes in which the front part is wider than the rear part.
7 visible rings, the 5th one is much darker.

Whole body covered in tufts of dark hairs that are slightly longer on the sides.
At the lower end of the abdomen, 3 plumes of long, lanceolate bristles converging toward the rear end.

They stand on end and form a fan when larvae feel endangered.
That feature is characteristic of all the species of the Anthrenus genus.

Colour    

Dark yellow to brown, sometimes turning black.
Rather orange-coloured head.

Development cycle

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A. verbasci development generally requires 200 to 350 days from the egg-stage to the adult stage, and there can be 1 or 2 generations per year depending on ambient thermo-hygrometric conditions.
Such optimal conditions are only found in heated places (30°C). Conversely, in less favourable or even extreme conditions, the development cycle can last up to 2 years or more.
In summer, females frequently get into houses to lay their eggs; that is when they are visible on window panes or around windows.


After mating, females lay between 20 and 200 eggs on the various substrates (cf. Infested Materials) that are to become the larvae’s food and shelter.
After between 1 and 2 weeks’ incubation, new-born larvae start feeding and causing damage. The number of larval stages varies, from 5 or 6 on an average up to 29. Larval development very much depends on temperature and on the nutrient richness of the medium.


It can last only a few months in optimal conditions, but several years on unfavourable media. Then larvae turn into nymphs, which are rather short and a yellowish colour. Nymphosis lasts 8 days at 30°C and about 24 days at 24°C. However, once the insect has reached the adult stage, it still lives inside the nymph for up to one week before taking flight.

 

Infected materials

Insect collections are particularly affected by A.verbasci. Its food diet also includes all animal matter by-products (wool, skin and even carpets and carpeting).
Wheat, flour and even some pharmaceutical or drugstore products can be infested by their larvae.

The species is often found on rat-poisoned wheat spread around to fight rodents.
In natural environments, larvae mainly develop in birds’ nests where they feed on feather and hair fragments.

  • Dégradation observée sur un oiseau naturalisé (Epervier d'Europe) Attaques des os et des plumes

  • Contenu d'un cocon d'araignée dévoré par les larves d'A.verbasci

Geographical distribution

Worldwide distribution, but mostly present in temperate regions.