Sierra Nevada Insects and Spiders
Hymenoptera, Family Orussidae

Orussids are interesting sawflies that are relatively rare.  Unlike all other sawflies, whose larvae are phytophagous, the larvae of orussids are thought to feed on or to be parasitoids on the larvae of wood boring beetles in the family Buprestidae.  The parasitoid habit is similar to that of many genera in the suborder Apocrita.  Female orussids are found running up and down the trunks of old dead trees and stumps that are devoid of bark while using their antennae to detect beetle larval activity within.  Once a likely spot is detected, the orussid will use her ovipositor to drill into the burrow or onto the beetle larva and lay an egg.  There are two species in California, Orussus occidentalis, shown above with a pseudoscorpion clamped to its right rear leg, and Orussus thoracicus.  These insects are surprisingly difficult to photograph.  They have a nasty habit of making sudden crab like movements to one side or the other that seem to be especially designed to provide the photographer with an out of focus image.
Female of Orussus thoracicus ovipositing.

Female of Orussus occidentalis ovipositing.

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