Nicobium castaneum (Olivier, 1790)

Synonym(s) : 

Anobium fasciatum Dufour, 1843
Anobium tomentosum Mulsant et Rey, 1863

Common names

  • Vrillette des bibliothèques
  • Library beetle
  • Tarlo de las bibliotecas
  • Nagekäfer


  • Order:  Coleoptera
  • Family:  Ptinidae
  • Genus:  Nicobium
  • Species:  castaneum

Frequency index:

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Nicobium castaneum beetles are the borers that cause most damage in precious book collections, parchments, cardboards, wooden furniture and wood-panelling (whether from resiniferous species or not).
They are preferably found in heated places: houses, storage places, museums…

Recognition criteria



4 to 6 mm long


Characteristic aspect, sturdy body, sharply convex elytra. When at rest, head and thorax more or less at a right angle with elytron axis.
Head partly covered by the pronotum, which is quite prominent. Fairly long antennae, last 3 articles bigger and more or less serrate.
Elytra are striated lengthwise by rows of pits, and covered in a double short pubescence (flat and erect).


Uniformly reddish brown. Golden pubescence on elytra



5 to 7 mm long.


Look like small arched grubs with a scarce hairiness on their whole body. Legs are quite visible.
Head armed with powerful mandibles


Yellowish white ; brown mouthparts

Development cycle

The biology of that species is close to that of the common furniture beetle (Anobium punctatum) (cf. fact-sheet).
Adults are good fliers. They take to the air from spring through September, with an emergence peak 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); which are a milky-white colour, hard enough to spot due to their very small size (about 0.5 mm). Eggs are laid in several steps, in cracks in the substrate, in wood vessels or in former galleries.
Incubation lasts about 1 month; new-born larvae immediately bore new galleries to start feeding.

Larval faeces are characteristic, never powder-like, but small-peanut-shaped, which e to differentiate them from the faeces of larvae from other species (Lyctus brunneusL. linearis and Hylotrupes bajulus) (cf. fact-sheets) which can infest the same substrates.
Larval development length very much depends on the nutrient quality of the base, on temperature and on ambient hygrometry. It can last between 8 and 36 months, and up to ten years if conditions are not favourable.

At the end of their development, larvae build themselves visible, quite tough pupal cells near the surface of the nutrient material, which can partly remain long after imagoes have taken flight. Adults’ exit holes are nearly circular.
Development is optimal when temperatures are around 22°C, with relative humidity between 55 and 60%.
Adults live about 1 month, sometimes longer.

Infected materials

Library beetles mostly infest white, soft wood but can also feed on resiniferous wood if needs be, along with all sorts of worked woods.
They very often infest furnishing, works of art and sculptures of our heritage.
They also feed on old documents, and on all paper or cardboard bases.
Parchments and leather bindings are sometimes literally eaten up by larvae.
Adults do not cause any direct damage.

Geographical distribution

Library beetles are not found in the tropical regions of Africa, Asia and South America. They have a typically holarctic distributio