While searching the open red-cedar woodland at Oklahoma’s Wichita Mountains National Wildlife Refuge back in September, I rather regularly encountered these darkling beetles (family Tenebrionidae) that I recognized as the species Eleodes tricostata. I really wanted to photograph the first several that I found, but I soon abandoned this idea because they just… wouldn’t… stop… crawling! Not that I’m impatient and couldn’t wait one out if I put my mind to it, but what I was really after was more photos of the beautifully black Cicindelidia obsoleta vulturina (Prairie Tiger Beetle) population that I had just found there. It would take most of the afternoon before I finally got the nice, closeup photos of the tiger beetle that I wanted, and as I started to leave the site I found yet another of these darkling beetles… just sitting there! The beetle didn’t move at all as I took first a few lateral profiles, then moved around to the front for the face shots that I so love, and finally back to the side for even more profiles. I was even able to remove the stick that the beetle had siddled up against to improve the composition of the profile shot and then place it behind the beetle as a backdrop in the frontal shot. Another lesson in why it pays not to waste too much time with uncooperative subjects when others are available.
I already knew about this species because I have encountered it several times before in my travels across the western states, but most memorably during my first visit to the Great Plains back in 1986 when I saw large numbers of this species and the related E. suturalis crossing the highway in front of us during the early evening hours in south-central Kansas. I’d never seen such en masse movement by large beetles, and although I’ve seen both of these species numerous times since I’ve not seen another such migration. Eleodes is the largest genus in the family in North America but occurs exclusively in the western states. Famous for their skunk-like head-stand when disturbed, Triplehorn et al. (2009) note the genus name is derived from Greek and means “olive-like.” This is certainly the case for most of the other members of the genus—mostly black and shiny, the larger species resemble “black olives with legs”; however, this species has not quite such aspect. Rather, its dull color, depressed fusiform shape and elytra with distinct, tuberculate costae (Triplehorn et al. 2009, Bernett 2008) make it immediately recognizable amongst the dozens of congeners that are likely to be found co-occurring with it in the different parts of its wide range.
Although the normal range of this species covers the Great Plains from Canada to Mexico, its eastern limit of distribution is still incompletely known. There are some historical records from western and central Iowa, but it was only recently that Maxwell & Young (1998) reported the species for the first time from east of the Mississippi River in Wisconsin. Seeing this report made me wonder if I might be able to find the species in Missouri also; however, those authors noted that the Wisconsin population was encountered exclusively in open habitats with exposed soil surfaces and sandy soil in close proximity to shrub and tree cover. No such habitat exists in western Missouri, and although tiny remnants of sand prairie habitat remain in the southeastern lowlands of the state they lack significant shrub and tree cover and are instead vegetated primarily by grasses and forbs.
Bernett, A. 2008. The genus Eleodes Eschscholtz (Coleoptera: Tenebrionidae) of eastern Colorado. Journal of the Kansas Entomological Society 81(4):377-391.
Maxwell, J. A. & D. K. Young. 1998. A significant eastern range extension for Eleodes tricostatus (Say) (Coleoptera: Tenebrionidae). The Coleopterists Bulletin 52(1):90–92.
Triplehorn, C. A., D. B. Thomas, and E. G. Riley. 2009. The genus Eleodes Eschscholtz (Coleoptera: Tenebrionidae) in Texas. The Coleopterists Bulletin 63(4):413-437.
Copyright © Ted C. MacRae 2012
6 thoughts on “Black olives with legs”
I am not quite clear on understanding the concept of “tuberculate costae.” Am I to understand that this is referencing that the parallel “ribs” running the length of the elytra are bumpy or wart-like?
See – you understand perfectly 🙂
I normally try to minimize or at least define the technical terms but lapsed this time. Thanks for letting me when I do this.
I enjoy your photos and info-always something to learn!
Ted, I love your articles. It really helps us amateurs to understand beetles better!
Hi Lillian – I’m glad to hear that. My hope is that both specialists and non-specialists find something interesting in my posts.