Scarab Hunter Wasps on the Baccharis
Location: Elyria Canyon Park, Mount Washington, Los Angeles, CA
October 14, 2012
In Los Angeles, we enjoyed our first (and early) rain of the season, and the weekend following is gloriously sunny and warm, but not too hot. It seemed like a good day to visit the Baccharis in Elyria Canyon Park, camera in hand. Soon after arriving, we photographed this large, nervous wasp that we thought might be a Scarab Hunter in the family Scoliidae, a hunch that eventually proved correct after returning home and checking BugGuide.
By the time we set the camera to macro feature and waited for the lengthy recording time, we managed to get two good photos and several less than ideal images. A few minutes later, we noticed a more orange individual. It should be noted that these are large wasps, at least 1 1/4 inches in length and easily twice as big as a Honey Bee. As we moved closer to the more orange individual, it was buzzed by a more yellow individual that may or may not have been the individual we had just photographed.
The first thought that entered our mind was “could these be sexually dimorphic individuals of the same species?” Well, that thought turned out to be accurate when we returned home and identified these Scarab Hunter Wasps as Campsomeris tolteca on BugGuide. Alas, there is no species specific information on Campsomeris tolteca, but according to the data page, the species is reported from California to Texas along the border states. The male images on BugGuide match our male and the female images on BugGuidematch our female.
Despite the lengthy record time, we managed to get two shots of both individuals together before the male flew off. We then got several nice images of the female.
The best place we have discovered to read about the Scarab Hunter Wasps is on our contributor Eric Eaton’s blog, BugEric. According to BugEric: “Campsomeris wasps belong to the family Scoliidae, all of which are known parasitoids of scarab beetle grubs. A parasitoid is a parasite that invariably kills its host. Female scoliids, with their heavy, spiny legs, dig up a scarab grub, sting it into brief paralysis, and then lay a single egg on the beetle larva. Then the wasp leaves the scene. The grub eventually regains consciousness and control over its motor skills (such as they are), resuming its underground existence feeding on the roots of plants. Meanwhile, the wasp egg hatches and the wasp larva begins feeding as an external parasite of the beetle grub.”
Here is one final image of this impressive Scarab Hunter Wasp.