Three diagnostic characteristics are visible in close-up photos:
• The antennae arise below the eyes, under a ridge of exoskeleton. (1)
• The head between the eyes bears a number of pyramidal bumps or spikes. (2)
• The wing has a single submarginal cell, a feature not easily seen in field photos because Orussus folds its wings tighlty over its back. (3)
• Female Orussus can be identified by the swollen antenna tips, visible in this image.
Occasionally I saw two individuals notice each other from several feet apart, approach, then scuttle or fly off (4).
I also observed many individuals tapping the log surface with their antennae (5). Lars Vilhelmsen, Natural History Museum of Denmark, University of Copenhagen, and colleagues have shown that in females, vibrations in the wood caused by the antenna taps are pecieved by the forelegs. Females use this vibrational sensing to find suitable locations for ovipositing. (Vilhelmsen web site)
I occasionally observed individuals backing into holes in a log. (6) Vilhelmsen informed me by e-mail that this is a male, probably just hiding. Note that the individual peeks out twice after entering the hole.