During last year’s Fall Tiger Beetle Collecting Trip, I visited several rural cemeteries in northeastern Texas. No, this was not a diversion from my beetle collecting—cemeteries in rural areas can be great places to look for tiger beetles because they tend to be lightly managed parcels of land of low agricultural value, thus retaining to some degree the character of the original landscape. In this case, the cemeteries I visited were located in the northern part of Texas’ Post Oak Savannah, a transitional ecoregion with uplands characterized by deep sandy soils supporting native bunchgrasses and scattered post oaks. It is the open, sandy areas in this region where distinctive subspecific populations of two more broadly distributed tiger beetles can be found—Cicindela scutellaris rugata and Cicindela formosa pigmentosignata. One location where I looked for them was an old cemetery in Henderson County. Within minutes of stepping out of the car, I found the first subspecies—unmistakable by its solid shiny blue coloration.
Cicindela scutellaris rugata, dubbed the “wrinkled tiger beetle” by Erwin & Pearson (2008), is one of seven recognized subspecies of this widely distributed species that shows greater geographical variation than any other species of tiger beetle in North America (Pearson et al. 2006). Across its range the species is found in deep, dry sand habitats that are fully exposed to the sun and lack any standing water. Except in the far southeastern U.S., this species is often found in association with C. formosa (although in Missouri I have noted that C. scutellaris occurs slightly earlier in the spring and slightly later in the fall—perhaps at least in part to avoid direct competition with and possibly even predation by that larger species).
This subspecies is similar in appearance to C. s. unicolor, distributed across the southeastern U.S. and separated from C. s. rugata by the Mississippi River floodplain—both are shiny blue to blue-green in coloration and exhibit no maculations on the elytra. However, C. s. rugata has a more wrinkled pronotum (hence, the subspecific epithet) and smoother head, while C. s. unicolor has a smoother pronotum and more wrinkled head. Another subspecies, C. s. flavoviridis, shares this surface sculpturing but differs in having the elytra colored lighter yellow-green—in this sense C. s. rugata can be considered intermediate between C. s. unicolor to the east and C. s. flavoviridis to the west (Vaurie 1950). Cicindela s. rugata can also be confused with immaculate forms of C. sexguttata (six-spotted tiger beetle), but the latter is less robust with a more tapered posterior, and both sexes of C. sexguttata have a whitish labrum (in all subspecies of C. scutellaris only males have a white labrum, while females have a dark to black labrum).
As I have noted for other C. scutellaris subspecies that I have encountered (nominate as well as C. s. lecontei, C. s. yampae, and Missouri’s intergrade population of C. s. unicolor x C. s. lecontei), adults were fairly abundant during the late morning hours but largely disappeared during the afternoon, probably having dug into their burrows to escape the midday heat (although I did not search for the burrows and dig them out as I have done for the other mentioned subspecies). I did see a very few individuals at another sandy cemetery in neighboring Van Zandt Co. that I visited later in the afternoon (and at both locations I found the stunning C. formosa pigmentosignata—that will be the subject of another post).
Erwin, T. L. & D. L. Pearson. 2008. A Treatise on the Western Hemisphere Caraboidea (Coleoptera). Their classification, distributions, and ways of life. Volume II (Carabidae-Nebriiformes 2-Cicindelitae). Pensoft Series Faunistica 84. Pensoft Publishers, Sofia, 400 pp [Amazon description, book review].
Pearson, D. L., C. B. Knisley & C. J. Kazilek. 2006. A Field Guide to the Tiger Beetles of the United States and Canada. Oxford University Press, New York, 227 pp. [Oxford description].
Vaurie, P. 1950. Four new subspecies of the genus Cicindela (Coleoptera, Cicindelidae). American Museum Novitates 1458:1–6 [AMNH Digital Library pdf].
© Ted C. MacRae 2016
9 thoughts on “Cicindela scutellaris rugata (the “wrinkled tiger beetle”)”
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Beautiful beetles and great photos. Merry Christmas, Ted!
Merry Christmas to you as well, Adrian!
In the “farEast” (Vermont), we quite commonly see scutellaris lecontei with formosa generosa.
Typo – should be “far southeastern”.
Great pictures, and an interesting idea to prospect for insects in cemeteries. I would worry about violating some rule, but I guess it can be ok.
I visit old rural cemeteries whenever I see them – not just when collecting – because I am interested in them from a historical context also. In all my visits I’ve never been approached or even seen anybody. I’m not too concerned that I’m doing anything wrong as long as it is not signed “Private.”
This has been a very interesting story, and through it I have learned that our local metallic green tiger beetles are probably C. sexguttata. Hardly a huge revelation, but that is progress for me.
One of my goals for the coming summer is to get good pictures of this lovely insect.
The metallic colors must be a structural color, which is generally where light enters a microscopic labyrinth and various wavelengths are selectively cancelled. Only certain wavelengths escape the labyrinth, and those reflected colors are what we see. So the differences in subspecies and species here would be due to extremely minute differences in whatever labyrinth structures are in the cuticle.
Mark, I’m glad you’ve found these posts interesting. I’m not sure where you are located, but Cicindela sexguttata is probably the most commonly encountered “green” species in eastern North America.
If you’re interested in more information about the structural coloration of tiger beetles, Schultz & Rankin (1985) provide some detail about this.