Graphisurus triangulifer in Missouri

Graphisurus triangulifer | Sam A. Baker State Park, Missouri

Of the three species of the genus Graphisurus occurring in Missouri, G. triangulifer is both the most attractive and the least commonly encountered.  Back when I surveyed the Cerambycidae of Missouri (MacRae 1994), I examined only 45 specimens of this species in the major public and private collections of the state, compared to slightly more of the equally uncommon G. despectus and a whopping 271 of the übercommon G. fasciatus.  Nearly all of the specimens I examined of this species were encountered at lights, and it has been in this manner almost exclusively that I have seen the species for myself.

The species is named for the dark triangular markings on the elytra.

The individual in these photos was seen at Sam A. Baker State Park in the southeastern Ozark Highlands of Missouri during early July, and—like most of the others I have seen—it was attracted to my blacklight. I really don’t like photographing insects directly on the white landing sheet that I use for blacklighting, so I moved the beetle to the trunk of a nearby boxelder tree (Acer negundo) for a more natural looking background. There are a few reports of the species utilizing Acer for larval development (Lingafelter 2007), so this could be a very natural setting; however, I have not seen any actual records of the species being reared from that host. More often the species has been recorded breeding in dead sugarberry (Celtis laevigata). While I have conducted many rearings from Celtis, I’ve not yet succeeded in rearing this species—I suspect it probably breeds in larger diameter branches given its relatively large size (12–17 mm in length).  This idea is bolstered by the fact that the one adult that I did not encounter at lights was found on the trunk of a large, dead sugarberry near San Antonio, Texas.  Hoffman et al. (2002) noted that the species exhibits a southern, lowland distribution extending from Long Island to central Georgia, thence west to Texas and northward in the interior as far north as Ohio and Indiana (it has also been recorded from Kansas and, of course, Missouri).  This distribution pattern agrees largely with that of Celtis laevigata in the eastern U.S., suggesting that this plant may indeed be its primary host.  A fairly restricted host range for G. triangulifer would not be unexpected, since each of the other two species in the genus also exhibits a fair degree of host fidelity—G. despectus breeds almost exclusively in hickory (Carya spp.), while G. fasciatus breeds primarily in oak (Quercus spp.).

REFERENCES:

Hoffman, R. L., S. M. Roble, and W. E. Steiner, Jr. 2002. Thirteen additions to the known beetle fauna of Virginia (Coleoptera: Scirtidae, Bothrideridae, Cleridae, Tenebrionidae, Melyridae, Callirhipidae, Cerambycidae, Chrysomelidae). Banisteria 20:53–61.

Lingafelter, S. W. 2007. Illustrated Key to the Longhorned Woodboring Beetles of the Eastern United States. Coleopterists Society Miscellaneous Publications, Special Publication No. 3, 206 pp.

MacRae, T. C. 1994. Annotated checklist of the longhorned beetles (Coleoptera: Cerambycidae and Disteniidae) known to occur in Missouri. Insecta Mundi 7(4) (1993):223–252.

Copyright © Ted C. MacRae 2011