Xylosandrus crassiusculus

Black Stem Borer

Xylosandrus germanus, Ambrosia Beetle photo

Family: Curculionidae

Subfamily: Scolytinae

Length: 2.0-2.5 mm


There are four Nearctic species of Xylosandrus, all of them found in eastern North America. Three of the four (including this one) are native to Asia.

In Xylosandrus crassiusculus, look for shallow punctations on the front of the insect. The elytra boast yellow setae, most pronounced on the declivity. The elytral striae are not pronounced, except that they are deep on the declivity.

Xylosandrus beetles excavate into the twigs and branches of healthy trees. They typically do not kill the trees, but reduce their vigor and make ornamental trees less attractive.

Xylosandrus crassiusculus is an Ambrosia Beetle, excavating galleries in wood and cultivating fungi for the larvae and adults to feed on.

This genus has an interesting life history when it comes to sex and gender. The females are 1.5x to 2x the length of the males. Unlike the females, males are flightless, and in fact they are seldom found outside the ambrosia gallery. When female larvae mature into adults they mate with their brothers and then fly off to start an ambrosia gallery of their own.

Insects of West Virginia