As much love as I give to tiger beetles, I tend to be just as indifferent to the non-cicindeline ground beetles. Why this is I don’t know; ground beetles sensu lato are super diverse taxonomically, morphologically, and ecologically, and the colors of some rival even the gaudiest of beetles. Still, whenever I see a Harpalus pensylvanicus or Bembidion affine crawling on the ground, my brain just yawns and I look elsewhere. I suspect my tiger beetle inclinations have more to do with their extreme habitat specificity and attendant behavioral adaptations, in which areas the other ground beetles are clearly somewhat lacking. There are also those tiger beetles jaws!
Well, there is one group of carabids that does excite me almost (almost!) as much as tiger beetles, and that is the nominate subfamily Carabinae with genera such as Calosoma, Callisthenes, Scaphinotus, and Cychrus—the so-called “caterpillar hunters” and “snail hunters.” These are the giants of the family, with most species measuring at least 15 mm in length and many measuring up to 25 mm in length or more. And then there are those jaws! Perhaps my feelings for this group are no coincidence, given the close relationship between these beetles and tiger beetles (in fact, most molecular data suggest that tiger beetles are firmly nested within the Carabinae).
I came across several individuals representing Calosoma sayi (black caterpillar hunter), including the two individuals shown in the above photographs, back in late August under street lamps in the southeastern Missouri city of Portageville. Though it lacks the metallic colors possessed by many other species in the group, it does have those delightful, sculptured jaws. While I don’t normally like to photograph beetles on pavement, that’s where the beetles were and I’ve had poor luck in trying to move active beetles to an alternative substrate and then get them to settle down and resume natural-looking positions. In this case, it turned out not to be necessary to move the beetles, as the color and texture of the pavement provides a very nice background for these all black beetles. Also, did I mention those jaws?!
Copyright © Ted C. MacRae 2012