Oligomerus ptilinoides (Wollaston, 1854)
The Oligomerus genus comprises 3 species in France, but only O. ptilinoides are anthropophilic and harmful. They are indeed dangerous xylophagous insects quite frequently found, amongst others, within the whole Mediterranean basin (south of France, Spain, Tunisia, Egypt, Turkey…). They are attracted to ultra-violet light.
Critères de reconnaissance
|5 to 7 mm long|
The pronotum nearly completely covers the head; it is sharply rounded, and as wide as the elytra. At rest, head and thorax are more or less at a right angler with the elytral axis.
Brown to reddish brown, pronotum usually slightly darker than elytra.
|6 to 7 mm long|
Arched, with scarce hairiness. Legs quite visible.
Creamy whitish; light brown head, blackish mouthparts. Light-coloured legs.
Cycle de développement
The biology of that species is fairly close to that of other Anobiidae (Anobium punctatum and Nicobium castaneum) (cf. fact-sheets). However, Oligomerus ptilinoides is strictly xylophagous whereas other borers can develop to the expense of more diversified materials (books, paper, archives).
Adults are good fliers. They are active from early spring through September, with increased emergence in July and August.
That is when small heaps of faecal bore-dust can be seen at the level of infested materials
Females lay about 30 eggs on an average (many more in optimal conditions); of a milky-white colour, hard enough to spot due to their very small size (about 0.5 mm). Eggs are laid in several steps, over a several-week-long period, in wood cracks and vessels or in former galleries. Incubation lasts between 12 and 15 days. New-born larvae immediately bore galleries in the wood to start feeding.
As in the case of mo
st xylophagous insects, larval development length very much depends on the nutrient quality of the base, on temperature, on ambient hygrometry and on the presence of lignin-degrading fungi.
It can last between 8 and 36 months, even longer if conditions are not favourable. Development is optimal when temperatures are around 22°C, with ambient relative humidity between 55 and 60%, and when humidity inside the wood is between 11 and 16% with temperatures ranging between 20 and 32°C.
If humidity inside the wood is higher than 20%, larvae are often infested and killed by moulds.
Larval development is stopped when temperatures are below 12°C. Larvae can fast for about 3 months.
Nymphosis takes place under the wood surface, in spaces built by larvae. Adults’ exit holes are circular.
Average full cycle length (from egg to adult) is about 1 year in Mediterranean regions, and 2 or 3 years in more temperate climate zones.
Adults do not feed and do not cause any direct damage. They live about 4 weeks or a little more.
O. ptilinoides cause huge damage in furniture, statues, wooden works of art, in easel painting stretchers and paints on wood, in roof timbers,…
They are particularly dreaded in museums and individual housings containing old furniture, paintings and wooden objects. Most of the time they infest wood from deciduous species (elm, ash, oak, maple, apple-tree,…).
Damage is characterized by the presence of peanut-shaped dust pellets and of circular, 2- to 3-mm diameter exit holes.
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The species is only found in the palearctic region, North Africa included. It is not found in hot tropical regions (Asia, Africa, South America).
In France, Oligomerus ptilinoides is mostly found in the Mediterranean region.
Indice de fréquence : 4 / 5
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