This past spring I returned to the lowlands of southeastern Missouri in an effort to find and photograph a population of tiger beetles that seems to be unique to the area. The beetles represent Cicindela scutellaris (Festive Tiger Beetle), a widespread species that is common in dry sand habitats across the central and eastern U.S. It is also one of North America’s most polytopic species, with populations in the Great Plains, eastern U.S., Atlantic Coast, southeastern Coastal Plain, and several isolated populations on the western and southwestern peripheries of the species’ range of distribution recognized as distinct subspecies. In Missouri the species is known only from the extreme northwestern, northeastern, and southeastern corners of the state. In all of these areas the populations are found on alluvial sand deposits associated with the Missouri and Mississippi Rivers. Additional sand deposits are found in the areas between these three widely disjunct areas, but curiously the species has not yet been found in them, despite the presence of other species that occupy these same habitats such as Cicindela formosa (Big Sand Tiger Beetle).
The populations in northern Missouri fall well within the distributional range of subspecies C. s. lecontei and are readily assignable to that taxon based on their wine-red coloration and well developed elytral markings. The population in southeastern Missouri, however, cannot be assigned either to that subspecies or to the more southern subspecies C. s. unicolor, which occurs along the southeastern U.S. Coastal Plain and is characterized by solid green coloration and no elytral markings. Individuals from southeastern Missouri are typically green, as in C. s. unicolor, but usually exhibit a distinct wine overtone from C. s. lecontei that varies greatly in its degree of development. Like C. s. lecontei, the elytra are usually marked, but never as strongly as in C. s. lecontei and sometimes not at all (as in C. s. unicolor). The two individuals shown in these photos represent the typical condition—wine blushing and elytral markings only moderately developed; however, more extreme examples can be seen in photos from fall 2008 and spring 2009 (taken during my “point-and-shoot” days, which explains my desire to photograph these beetles again). The intergradation of characters, their variable development, and the apparent presence of a wide disjunction zone between this population and C. s. lecontei to the north suggest to me that it originated from a relatively recent hybridization event between C. s. lecontei and C. s. unicolor—perhaps during the post-glacial hypsithermal that ended some 5,000 years ago.
While I am happier with these photos than I am with those taken earlier, they don’t represent either the full range of variability seen in the population or the most aesthetically pleasing tiger beetle photographs I’ve ever taken. I made two trips to the southeast this past spring, and on each trip I was successful in finding and photographing only a single, very skittish individual—one on a sandy trail through upland forest (Holly Ridge Conservation Area) and the other along the margin of a sand blowout in a native sand prairie remnant (Sand Prairie Conservation Area). I’ll try again this coming spring and hopefully will be able to show some better photographs.
p.s. Can you tell the difference in the type of flash diffuser I used between these two trips? If so, which one do you like better?
Copyright © Ted C. MacRae 2013