Dendroctonus brevicomis
Western pine beetles "swimming" in oleoresin exuding from a pitch tube on the bark of ponderosa pine. The beetle (in center of picture) and its mate underneath were observed to burrow down through the viscous liquid into the entrance of the gallery (directly under and to right of beetles) for up to several minutes before returning and shoving out more resin. The resin is slightly toxic and may exhaust the beetles; it also may eventually crystallize to entrap them.
image (C) 1995 by John A. Byers