Although I’ve been collecting insects since I was a kid (and seriously for nearly three decades), it has only been in more recent years that fall has become an important part of the collecting season for me. With the notable exception of Fall 1978, when the Systematic Entomology course I was enrolled in sent me on a frantic quest to become one of the few undergraduate members of the exclusive “200 family” club (I got 205!), I long viewed fall as a time to hang up the net and begin the winter-long process of mounting, labeling, and curating the hundreds – sometimes thousands – of specimens I had collected earlier in the year during spring and summer. This has primarily been a reflection of my taxonomic interest – woodboring beetles in the families Buprestidae and Cerambycidae, which occur at their overwhelmingly greatest abundance and diversity throughout most of North America during spring and summer but are found only sparingly later in the season. Tiger beetles (family Cicindelidae) changed all that, and when I first began serious study of the group around 10 years ago, I found the combination of gorgeous weather and multitude of “spring/fall” species that emerge briefly during fall an irresistible siren call to the field. I’ve not looked back, and the Annual Fall Tiger Beetle Collecting Trip™ is now an established and eagerly anticipated event.
Cicindela obsoleta vulturina - the prairie tiger beetle (Blackjack Knob, Taney Co., Missouri).
No species embodies all that I love about fall tiger beetle collecting more than
Cicindela obsoleta vulturina, the prairie tiger beetle. I first learned of the occurrence in Missouri of this large, dark green species back in 2000, when I saw a single specimen in the
Enns Entomology Museum collected in Protem, Taney Co. I was just beginning my tiger beetle studies and would later learn what the Tiger Beetle Guild already knew – that the occurrence of this species in Missouri was restricted to cedar glade habitats in the White River Hills region in the extreme southwestern part of the state, and that the population occurring there and in adjacent northern Arkansas was disjunct by 300+ miles from the main population in Texas and Oklahoma. I couldn’t wait to see it for myself and eventually enlisted the help of
Eric Eaton, living in the area at the time, and asked him to let me know if he saw a large green tiger beetle after the late summer rains began. That September, I got a message from Eric saying that he had seen just such a beast not far from his home, and the following weekend he and I would enjoy the chance to meet each other in person and the splendor of the season while finding this marvelous species at several locations in the area. Thus began my love affair with this species, and for several years I returned to the area each fall to document additional localities for this and other tiger beetle species occurring in the area.
Blackjack Knob is part of an extensive xeric dolomite prairie complex (commonly referred to as cedar glades, though the term is not precisely accurate) in the White River Hills subsection of the Ozark Highlands, providing habitat for prairie tiger beetles and other typically southwestern plants and animals.
In fact, until a few weeks ago it had been several years since I had last seen this species in the field. I did make an attempt to see it again last year but returned home from that early October trip unsuccessful,
cold and wet. Thus, when tiger beetle enthusiast Steve Spomer mentioned to me earlier this summer that he wanted to see our Missouri population, I jumped at the chance to coordinate our visits this fall and show him some of my favorite sites. The Patron Saint of
Cicindela was smiling down upon us that day, as perfect timing and sunny skies combined to bring adults out in an abundance that I’d not seen in any of my previous visits. I would take advantage of this rare opportunity and spend the next day in the area as well, documenting a number of new localities along the northern and eastern edge of its known distribution, including a far eastern extension of its range to
Caney Mountain Conservation Area in Ozark Co. where we had long suspected the beetle to occur but failed in all previous attempts to find it.
Steve Spomer and yours truly at Cane Creek Rd. site.
The prairie tiger beetle is the easternmost subspecies of the large grassland tiger beetle, which along with its other included subspecies covers a geographic range covering most of Texas, New Mexico, and eastern Arizona and extending up through western Oklahoma and Kansas into eastern Colorado. Individuals of subspecies
vulturina, occurring primarily in eastern/central Texas, are distinguished from the other subspecies (nominate in western Texas and eastern New Mexico north into Colorado,
santaclarae in New Mexico and Arizona, and
neojuvenilis in south Texas) by their generally black to olive-green coloration and reduced, narrow elytral markings, typically with an inverted “V” at mid-elytron. The Missouri/Arkansas disjunct population is interesting from several standpoints:
- Individuals mostly dark olive-green – no black individuals.
- Elytral maculations more completely developed.
- Adults active in late summer/early fall rather than summer.
These features, in particular coloration and maculation, have fueled speculation that this isolated population might be subspecifically distinct (Pearson et al. 2006). A recent review of material from throughout its range found these color characters of limited use in unequivocally diagnosing individuals from the Missouri and Arkansas population as a separate subspecific taxon (Mawdsley 2009); however, a molecular systematics approach ultimately may be needed to resolve the status of this population. Presumably, the Missouri/Arkansas disjunct population represents a hypsithermal relict, left behind when the return of cooler, moister conditions caused a retreat of the formerly more expansive grasslands to their current position. If true, then the Missouri/Arkansas population has been isolated from the parent population for ~6,000 years. I suspect that the late summer/early fall adult phenology is an adaptation to local precipitation patterns, relying on more predictable late summer rains to trigger adult emergence after the generally droughty months of July and August. In this regard it differs fundamentally from the true “fall” species, which emerge briefly in the fall as sexually immature adults before overwintering and re-emerging in the spring for mating and oviposition. These Missouri/Arkansas disjuncts do not re-emerge in spring, but instead mate and lay eggs in the fall before the onset of cold weather. The eggs hatch as well (based on my growth chamber observations of this species), so winter also is passed as a larva – either as newly-hatched 1st instars, or as later instars that hatched during the previous year(s) – rather than as adults.
I have noted considerable variation in the coloration and maculations of individuals in this population. The individual in the first photograph above is typical of the population – dark olive-green with thin but nearly complete maculations. That individual comes from Blackjack Knob (Taney Co.), which is near the heart of the White River Hills region. However, the degree to which the maculations are developed is variable, ranging from rather incomplete to even more fully developed due to the presence of a marginal connection. Additionally, a few individuals can be found that show greater or lesser suffusion of brown on the head, pronotum, and elytra. At another location in the county closer to the northern distributional limit (Hwy 160/Cane Creek Rd.), this brown suffusion is more common and variably expressed from minimal to nearly complete. The photographs below show five individuals from this site expressing differing degrees of brown as well as the variable macular development seen throughout the population:
Male (Hwy 160/Cane Creek Rd.) - green w/ trace brown, marginal band incomplete, median band complete.
Female (Hwy 160/Cane Creek Rd.) - green w/ slight brown, marginal band complete, median band incomplete.
Male (Hwy 160/Cane Creek Rd.) - green w/ moderate brown, marginal band incomplete, median band incomplete.
Male (Hwy 160/Cane Creek Rd.) - green w/ heavy brown, marginal band complete, median band complete.
Female (Hwy 160/Cane Creek Rd.) - completely brown, marginal band complete, median band incomplete.
There is another site even further north in the county (Merriam Woods), which I found for the first time on this trip and, to my knowledge, represents the northernmost extent of the population in Missouri. At this site, nearly all of the individuals show coppery-brown coloration with almost no hint of green. These fully brown individuals seem to represent an appearance that is completely unlike that seen in any other part of the range of the species. The individual in the photo below typifies the appearance of the beetles seen at this site:
Male (Merriam Woods) - brown, marginal band incomplete, median band complete.
I’m less familiar with coloration of the population further south in Arkansas, although in my limited collecting in that area I recall that most individuals I encountered exhibited the dark olive-green coloration typical of individuals at Blackjack Knob and other more southern sites in Missouri. Thus, there seems to a clinal element to variability in coloration in the Missouri/Arkansas disjunct population. I suspect that the unique coloration of the beetles in this population is related to the soils with which they are associated. Light gray Jefferson City-Cotter dolomite bedrock forms the core of the White River Hills landscape and is exposed extensively in the glades that dominate its knobs and slopes. These exposures are weather-stained black and overlain by thin, black soils that support dark, green-black lichens amongst the sparse vegetation, as seen in the following photographs taken at the newly identified northeasternmost site at
Caney Mountain Conservation Area:
Thinly soiled dolomite exposures punctuate the glades in the White River Hills. Prairie tiger beetles are found in these exposures.
Dark green-black lichens encrust the thin black soils overlaying the dolomite exposures. Prairie tiger beetle adult coloration closely matches the coloration of the lichens and soil.
The glades and dolomite exposures where these beetles are found in the White River Hills and the dry oak woodlands that surround them have a characteristic look that is not seen once one leaves the area, and I have found many new sites for the beetle in the northern and eastern fringes of the region by stopping at locations where the roadside exposures had the right “look.” The variation in maculation and coloration seen in this population may be an indication that the population is still adapting to local conditions since becoming isolated from main population.
Currently, I have 3rd-instar larvae that I collected from their burrows at Blackjack Knob (adults mostly green) and Merriam Woods (adults mostly brown) and hope the rear them to adulthood next year. If I succeed in getting virgin adults from the two sites, I think it would be interesting to do some single-pair crossings and rear the progeny to see how coloration is expressed. A long term project, for sure, as these beetles probably require at least two seasons to reach adulthood, but rearing them is fun! A more difficult, yet far more interesting, project would be to secure virgin adults from the mostly black main population in Texas – or even the bright green, thickly-maculated santaclarae subspecies from Arizona – to see how interbreeding them with these Missouri disjuncts would affect coloration and maculation in their progeny – they could be some of the most unusual appearing large grassland tiger beetles ever seen (not to mention their tongue-twisting taxonomic moniker of Cicindela (Cicindelidia) obsoleta vulturina [Missouri disjunct] x obsoleta santaclarae!). Timing would be a difficulty, since the Texas and Arizona populations exhibit a more normal summer adult phenology, but it would be worth a try if I could secure a source of larvae for rearing. Anybody?
A male sports his impressive pair of choppers.
Photo Details (insects): Canon 50D w/ 100mm macro lens (ISO 100, 1/250 sec, f/13-22), Canon MT-24EX flash (1/4-1/2 ratio) w/ Sto-Fen + GFPuffer diffusers. Typical post-processing (levels, minor cropping, unsharp mask).
REFERENCES:
Mawdsley, J. R. 2009. Geographic variation in U. S. populations of the tiger beetle Cicindela obsoleta Say (Coleoptera: Cicindelidae). Insecta Mundi 0094:1–10.
Pearson, D. L., C. B. Knisley and C. J. Kazilek. 2006. A Field Guide to the Tiger Beetles of the United States and Canada. Oxford University Press, New York, 227 pp.
Copyright © Ted C. MacRae 2010
It’s been four months now since I went to the Glass Mountains of northwestern Oklahoma on a hunch to look for Amblycheila cylindriformis (Great Plains giant tiger beetle). The five adults that I brought back from that night are still alive in a terrarium of native soil, but to this point they have refused to lay eggs. Despite feeding them regularly with fat Maduca larvae, there is obviously still something they need that I am not providing. I’ve suspected that perhaps the terrarium that I have them in is too small, and I’ve also noted in the literature that larval burrows are often found clustered near the entrance of mammal burrows. With this in mind, I combined the native soil from three separate terraria into one larger, deeper terrarium, packed the soil lightly, and used a spoon to create an artificial mammal burrow entrance. Not long after placing the adults in their new home they began digging at the back of the burrow, eventually creating two separate tunnels leading in opposite directions (and fortunately against the container walls so that I can see inside the tunnels). I was optimistic at first that finally I had given them what they wanted, but since digging the burrows they’ve just sat in them. Perhaps they “know” that winter is coming and are just looking to hole up for now, so I suppose I’ll go ahead and place the terrarium in the 10°C incubator with the rest of my larval and adult rearing containers and wait until next spring to see what happens.
In the meantime, I thought I would share these recent photographs of one of them. I had been wanting to take photographs of this species in a white box, which I have used with a few other species to generate some rather striking photographs (e.g., Gromphadorina portentosa, Buprestis rufipes, Scolopendron heros, Eleodes suturalis). The photographs in this post might look like they were taken in a white box, however, they were not. I’ve been spending a lot of time lately trying to come up with a diffuser setup that is convenient for field photographs of wild insects in their native habitats. Kurt’s do-it-yourself concave diffuser and Alex’s tracing paper diffuser work great with the Canon MT-24EX Macro Twin Lite Flash and the Canon MP-E 65mm f/2.8 1-5X Macro Lens, but as I mentioned in a previous post they do not work so well with the Canon EF 100mm f/2.8 Macro USM Lens and its longer working distance… or so I thought! I’ve come up with a modified version of the concave diffuser that seems to be what I am looking for – it is easy to use, adds virtually no weight to the camera, is completely portable for field use, can be used with both the 65mm and 100mm macro lenses, and – best of all – costs virtually nothing. The photographs in this post were taken with the first prototype, and now that the basic design and general dimensions seem to work I’ll try to make a more durable version. It’s simply a larger version of the concave diffuser – I found some very thick polypropylene foam that is sturdy enough to hold its shape but flexible enough to curl back and over the top of the flash heads, where the corners are held in place by Velcro. Essentially it forms a large “soft box” type diffuser in front of both flash heads. I cut the bottom inch off of a a 500-mL polypropylene beaker, then cut that in half and cut out all but a quarter inch of the bottom to form a sturdy but transluscent frame to hold the polypropylene foam against the flash head bracket on the front of the lens. Right now the foam is held in place by tape, but hot glue should do a better job, and the diffuser bracket is attached to the flash head bracket with Velcro. The whole rig comes off in a flash and lays mostly flat in the camera bag.
If this diffuser proves successful, it will eliminate the need for the different flash head extender brackets that I was considering. I really didn’t want to go that route because even the cheapest models are rather costly, and all of them add bulk to the camera and create problems for those who need to switch lenses frequently (such as I do). Of course, the real test is – does it achieve the desired result? I’m quite happy with these initial photographs – the lighting is quite even due to the large “apparent” size of the light source, and the annoying double specular highlights that are the hallmark of the MT-24EX are much less apparent (though still slightly discernible). The closest shots are at 1:1, while those of the entire beetle are between 1:1.5 and 1:2. They are among the largest beetle species that I have photographed, so the range of magnifications used here pretty much covers the entire range that I typically use with this lens. Wildflowers often require smaller mags and longer working distances, so it remains to be seen whether this diffuser/lens combination will be useful for them as well. 
All of the photographs in this post were taken with the 100mm macro lens (ISO100, 1/250 sec, F16) and direct MT-24EX macro twin flash using this new diffuser. The beetle was placed on white filter paper and covered with a clear glass bowl until it settled against the side of it. Once the beetle was quiet, I gently lifted the bowl and used micro-forceps to gently tug its legs into more appealing positions – surprisingly this did not cause it to become alarmed and try to flee (as long as I didn’t accidentally brush against one of its antennae!). For the last photograph, I placed the beetle back in its terrarium and used the same techniques to get the beetle in a good position. 
Beetles In The Bush 