Eight-toothed Spruce Bark Beetle

• The males give off aggregation pheromones that recruit thousands of beetles onto the same tree: only a massive, simultaneous attack can overcome the resin defence of a healthy spruce.
• It carries blue-stain fungi that colonise the wood and block the transport of water, helping to kill the tree.
• The major storms and droughts of recent decades have triggered outbreaks in central Europe that have destroyed hundreds of thousands of hectares of spruce forest.
• It does not kill trees on its own: it inoculates blue-stain fungi, above all Endoconidiophora polonica, which overcome the tree's defences and make the attack lethal.
• It coordinates mass attacks with aggregation pheromones produced by the males; once the population passes a certain threshold, those collective attacks bring down healthy trees.
• The symbiotic fungi themselves give off volatile compounds that attract more beetles, an unusual case of chemical convergence across kingdoms.
• It has killed millions of hectares of spruce in Europe, and the outbreaks are put down to warming, drought and forest management that leaves stands vulnerable.
• In natural forests it is not a pest but a driver of forest succession.

Skeleton type

Invertebrate - chitin exoskeleton (insect)

Habitat and environment

Weakened, wind-thrown or freshly felled Norway spruce

Size at birth

Whitish oval egg under 1 mm

Gestation / incubation

The eggs hatch after about 7 days; a generation is completed in 6-10 weeks in central Europe

Litter / clutch size

Each female lays between 30 and 80 eggs in niches on either side of the maternal gallery

Sources consulted: Forest Research (Reino Unido) · Jirošová et al. (2022), Frontiers in Microbiology · Kandasamy et al. (2023), PLOS Biology · Wermelinger (2004) · Forestry Commission (Reino Unido), guia de sintomas de Ips typographus · ScienceDirect (Hughes 1989) · Science Advances, How colonial animals evolve · Wikipedia, Zooid · IPPC ISPM 27 DP 27 (Chararas 1962) · ScienceDirect, Ips typographus · Forestry Commission (Reino Unido) · EDDMapS, ficha European spruce bark beetle

Best time: Flight from late spring, when the temperature reaches 11-16 °C; one generation a year in the mountains and two in the lowlands