Last weekend I mustered up the courage to begin experimenting with the 1-5X macro lens with my new camera. I had played around with it a little, trying to get a feel for finding the subject (it seemed hard) and the working distance (it seemed close). Really though, no amount of fiddling around could take the place of taking it out into the field and using it. I found some ideal subjects to experiment with – springtime Acmaeodera. With more than 150 species, this is one of the largest genera of jewel beetles (family Buprestidae) in North America. This genus is in terrible need of revision – new species continue to be recognized on a regular basis from the desert southwest and Mexico, where the group reaches its greatest diversity. Only a handful of species, however, are found in the eastern part of the U.S.
One of the most abundant and widespread of these is Acmaeodera tubulus (first two photos). Measuring only 5-7mm in length, it is among the smallest members of the genus and can be recognized by its black color with bronzy sheen and 8 (usually) small, yellow spots forming two longitudinal rows on each elytron. Adults of this species feed on the petals of a great variety of flowers – this individual was feeding on the petals of eastern beebalm (Monarda bradburiana). The larvae of this species are wood borers in twigs and small branches of various hardwood trees – I myself have reared it from dead branches of green hawthorn (Crataegus viridis), several species of hickory (Carya spp.), hackberry (Celtis occidentalis), honey locust (Gleditsia triacanthos), walnut (Juglans nigra), eastern hophornbeam (Ostrya virginiana), willow (Salix sp.), and slippery elm (Ulmus rubra).
While not apparent from these photos, adults in flight have the appearance of small bees. The elytra of all Acmaeodera are fused and do not separate during flight as in most other beetles, which in this small species results in a profile during flight similar to that of a small halictid (sweat bee). There is another species in Missouri (A. neglecta) that closely resembles A. tubulus but which can be distinguished by its larger punctures, duller surface, and the yellow spots of the elytra often longitudinally coalesced into irregular “C”-shaped markings on each side. Acmaeodera neglecta occurs primarily in the south-central U.S., and in Missouri I have found it most often in glade habitats.
Another common (though much less so than A. tubulus), springtime Acmaeodera in the eastern U.S. is Acmaeodera ornata (last photo). This handsome species is distinctly larger than A. tubulus, usually around 8-11mm in length, and has a broader, more flattened appearance with a distinct triangular depression on the pronotum. The elytra have a bluish cast rather than the bronzy sheen of A. tubulus, and the spots on the elytra are smaller, more numerous, and more of a creamy rather than yellow color. No other species in the eastern U.S. can be confused with it, although there is a very similar species (A. ornatoides) that occurs in Oklahoma and Texas.
This species, too, is fond of a great variety of flowers – especially asteraceous species, with this individual photographed on the widespread (but unfortunately exotic) ox-eye daisy (Leucanthemum vulgare). The body is covered with numerous long, thin hairs which may function in pollination – enlarge the photo to see the large amount of pollen that has become trapped among the hairs of this individual. Despite its widespread occurrence across the eatern U.S., larval host records are almost non-existent for this species – limited to some very old (and not entirely reliable) reports of it breeding in hickory and black locust (Robinina pseudoacacia). I have not managed to rear this species yet, despite the large number of rearings I’ve done from a wide variety of woody species in Missouri.
Copyright © Ted C. MacRae 2009