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Cossus cossus L.
Trypanus cossus

Insecta, Lepidoptera, Cossidae .

Goat moth, Willow borer

Description, Biology, Life Cycle, Damage, Common Names, Images


[R]Description
- Adult: Large moth of 70 to 80 mm wingspan, greyish, with a massive body covered in hairs. The fore wings have a dull appearence; the hind wings, stocky, are hairy on their basal part (*) .
- Egg: Elliptical, reddish-brown with black longitudinal striae, 1.2 x 1.7 mm, very resistant.
- Larva: 90 to 100 mm. The young caterpillar is carmine pink; the colour is darker and more pronounced in older individuals. The ventral surface is light yellow, the head black with powerful mandibles (*) .
Glands joined to the mouthparts secrete an extremely smelly substance, similar to the smell of old leather or poor quality wine.
- Pupa: 50 to 60 mm, with crowns of sharp spicules which enable it to crawl towards the opening of the gallery just before emergence.

[R]Biology
- The caterpillar develops in the trunks of numerous fruit-trees: apple, cherry, pear, plum, olive and other deciduous trees such as sweet chestnut, elm (Ulmus), oak (Quercus), poplar (Populus), chestnut (Aesculus), lime (Tilia), maple (Acer).
- Adult: The moth flies at dusk and at night, at the beginning of summer. The female, due to a powerful oviscapt, inserts her eggs in clusters in the bark crevices. Average fecundity: 500 eggs.
- Egg: embryonic development lasts 12 to 15 days.
- Larva: the caterpillar lives in galleries which it bores under the bark, then in the wood of the host tree. It ejects a reddish granular mass formed of sawdust and frass mixed with silk which accumulates at the foot of the tree. At the end of its development, it builds a cocoon out of wood particles and pupates (*) .
- The pupal stage lasts about 1 month. The adult emerges, often trailing behind itself the exuvia which then remains stuck in the bark.

[R]Life Cycle
- The cycle of the goat moth takes at least 2 years.
- The moths appear from the end of June to mid-August. The young caterpillars which emerge from the eggs form galleries under the bark (*) then, the following spring, penetrate the wood and bore slightly ascending galleries. They stay in the gallery the next winter and pupate in spring.

[R]Damage
The very smelly "worm-dust" signals the attack. There are usually several caterpillars in the same trunk. The caterpillars penetrate deep into the wood and can even drill into the heartwood. Certain trees, such as elm, are extremely resistant. Fruit trees, particularly apple and cherry, are more sensitive, dying rapidly (*) . In orchards, the goat-moth generally attacks old infirmt or wounded trees in which the sap moves poorly.


[R]Common Names
DE: Weidenbohrer ES: Taladro rojo FR: Cossus gāte-bois IT: Rodilegno rosso, Perdilegno rosso PT: Lagarta cossus GB: Goat moth, Willow borer

[R] Images

  1. Cossus cossus L. Damage on cherry tree Trunk sawn transversally to illustrate destruction by larvae of the entire liber area.
  2. Cossus cossus L. Larva in its gallery It is preparing to weave its cocoon ; note the silk threads and the dry frass. The gallery has been opened to display the larvae.
  3. Cossus cossus L. Moth (Coutin R. / OPIE)
  4. Cossus cossus L. Damage on cherry .
    the tree suddenly dries up.
  5. Cossus cossus L. Pupa in its cocoon The cocoon has been opened to display the pupa.

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