Pin- and Shot-Hole Borers, Ambrosia Beetles

(Coleoptera: Scolytidae and Platypodidae)

(1) General Biology of Pin- and Shot-Hole Borers

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General Biology of Pin- and Shot-Hole Borers

The minute adults of both families are between 1 and 12 mm long, slender and often of black or brownish coloration. The adults tunnel radially into the heartwood of the host and create a system of galleries in which eggs are laid. The types of galleries made by the parents are species-specific. The larvae do not feed on wood, but live on a fungus that they cultivate on the gallery walls. The Ambrosia fungus, a yeast, smells a bit like beer and therefore the beetles are also called Ambrosia beetles. The scent acts as an allelochemical that attracts even more bark beetles to the infested tree. Once the larvae are fully grown, they pupate inside the galleries. The newly hatched adult beetles leave the system of galleries through the entrance hole made by their parents and fly off for mating. The life cycle takes about 14 weeks for larger species and 3 to 4 weeks for smaller species.

Pin- and Shot-Hole Borers: (left bottom) newly hatched larva; (left top) young larva; (right top) fully fed larva; (right bottom) pupa (reproduced from Roberts, H., 1987)

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Michael F. Schneider, 1999