Yesterday I observed a crawling water beetle (Peltodytes species) attacking a damselfly larva. I was informed by one of our members (Tim) that Peltodytes are considered herbivorous. So I thought I’d post some photos I took during the attack, as well as a description of what I observed.

The other day, when I went out to collect some aquatic bugs to photograph, I forgot to take my specimen jars with me. All I took with me was a single large jar. I ended up collecting two damselfly larvae and two Peltodytes crawling water beetles (all of which went into the single jar). I photographed the bugs over a period of 2 days (one damselfly larva on day 1, the other bugs on day 2). During that 2-day period, I kept the bugs together in a Pyrex plate with water and some plant matter in it. On the second day, I took the second damsel from the Pyrex plate and placed it in a mini-aquarium that I use to photograph aquatics. In coloration, the damsel had become much paler than it had been the day before -- when I collected it, its color was a distinct, almost bright green. I thought it might have very recently molted, although I didn't see any effluvium. I took some photos and checked them on my computer. On doing so, I was shocked to discover that two of the damselfly's legs had been cleanly cut off. It was also missing 2 gills; I considered the possibility that I might have damaged the gills when I collected it, but I thought that was unlikely. I knew I could not have done anything to cause the injuries to its legs. I decided not to continue photographing the damselfly, because it was so damaged. Without removing the damselfly from the mini-aquarium, I then placed one of the crawling water beetles into the same mini-aquarium to photograph it. The beetle began to attack the damselfly. It used short, quick attacks -- it would dart in, apparently take a bite, then quickly dart away. I observed four or five such attacks. After each attack, the damselfly would turn toward the beetle, as if to counterattack it. At one point, the damselfly seemed to assume a more aggressive posture, as if to initiate an attack itself. The beetle's speed and agility were too much for the damselfly. The beetle seemed free to attack the damselfly at will, although the beetle apparently could not inflict very much damage on any given attack. All of the attacks that I observed were directed to the damselfly's left side. (I wonder whether the beetle was trying to further immobilize the damselfly by attacking the legs on the left side of the damselfly's body.) At no time did the beetle appear to be in any danger. After the fourth or fifth such attack, the damselfly tried to escape by attempting to crawl up the side of the glass.

This shot shows the beetle making a getaway after making one of its hit-and-run-type attacks. After taking a few such shots, I removed the damselfly from the mini-aquarium and placed it in its own specimen jar. Unfortunately, I was not able to get very good shots of the beetle on the attack. I would guess that each attack lasted no more than half a second. By the time I would snap a shot, the beetle would be speeding away. The morning following these attacks, the damselfly was quite active, and its coloration seemed to be returning. I think it might survive its injuries. All the bugs that I collected that day have been returned to their habitat (a small borrow pit/sump hole). I have posted five photos of this beetle in a separate post on BugGuide. -- Cat