beetles

Missouri’s disjunct population of Cicindela obsoleta vulturina

/ Ted C. MacRae / 18 Comments

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

“Colorfull Cockroach” discovered in Panama

/ Ted C. MacRae / 11 Comments

I won’t call this a taxonomy fail, since Patrick is clearly not a taxonomist, or even the first person to confuse a beetle with a cockroach.  Nevertheless, I was amused at Patrick’s amazement with the “colorfull cockroach” that he found and his palpable excitement that it might be a new discovery.

Well, I was amazed about this type of cockroach so, I would like to know if it is a cockroach or what because I know you guys will be also interested about checking out this type of bug.
Thanks please answer fast 🙂
Maybe is a new kind of cockroach not discovered yet.

Fortunately, the folks at What’s That Bug were able to correctly identify this as Euchroma gigantea (giant metallic ceiba borer), a beetle in the family Buprestidae (and the largest such species in the Western Hemisphere).  An interesting note about this photo is that it shows the beetle with some – but not all – of the green pulverulence (dusty coating) that these beetles exhibit over the elytra upon emergence from their host tree.  This coating is quickly worn off as the beetle goes about its activities, and most museum specimens of the species lack it completely – giving the beetle a purplish appearance as seen on the left elytron of the beetle in this photo.  Even handling a freshly-emerged specimen to mount it on an insect pin would likely result in loss of much of the coating, so it is quite difficult to preserve specimens in their lime-green dusty state.

Copyright © Ted C. MacRae 2010

Sweet Sixteen!

/ Ted C. MacRae / 16 Comments

The 7th Annual Fall Tiger Beetle Trip™ is officially over – Chris and I rolled back into town a little after midnight last night. It was an amazing trip – perfect weather, unparalleled scenery, and a record-breaking 16 species of tiger beetles seen in 13 localities across four states. Not only does this beat my previous trip record of 13 species, but we did it with only five days in the field. At the time of my previous update, we had visited several locations in the South Dakota Badlands and Nebraska Pine Ridge and found ten different tiger beetle species, including Cicindela pulchra (beautiful tiger beetle) – our top priority for the trip – C. nebraskana (prairie long-lipped tiger beetle), and C. lengi (blowout tiger beetle). Our plan for the next day was to visit the Badlands of Wyoming to look for C. decemnotata (Badlands tiger beetle – appropriately) and the Yampa River Valley of northwestern Colorado to look for C. scutellaris yampae and C. formosa gibsoni, all three of which we managed to find (though with caveats – stay tuned). Our originally planned final field day was to take us back into Wyoming to look for C. longilabris (boreal long-lipped tiger beetle) in the mountains east of Laramie and the Nebraska Sand Hills to look for the delicate little C. limbata before heading back home. However, we were finally paid a visit by “the skunk” and did not see any of these species (although our sighting of C. limbata (common claybank tiger beetle) in Wyoming did officially break the old trip record). Not wanting to end the trip on a disappointing day, we delayed our departure for home yesterday and visited two more sites at the eastern edge of the Nebraska Sand Hills (sites M and N in the above map) – a clay bank site where we saw a robust population of C. denverensis (to augment the single individual we had seen earlier in the trip) and several C. splendida (splendid tiger beetle), and another sand dune/blowout system where we at last succeeded in finding C. limbata.

The day after the end of the Annual Fall Tiger Beetle Trip™ is usually a somewhat depressing day for me. Not only is the trip over, but likely so is the entire insect collecting season. I know I need the down time to process the specimens and knowledge acquired during the season, but the field work itself remains my favorite aspect of this pursuit. Nevertheless, the experiences from this trip will fuel my memories for years to come, and in the next weeks I’ll share some of the stories that unfolded. Until then, I leave you with this portrait of C. pulchra – looking rather annoyed with me for my persistent efforts to take his photograph.

Cicindela pulchra - the ''beautiful'' tiger beetle

Copyright © Ted C. MacRae 2010

2 days, 6 localities, 10 species…

/ Ted C. MacRae / 6 Comments

Here’s an updated itinerary for the 7th Annual Fall Tiger Beetle Trip that fellow cicindelophile Chris Brown and I are in the midst of. We’ve spent the past two days visiting six localities in Nebraska and South Dakota. So far, we’ve found a total of 10 species – including every species we had hoped to see at this point in the trip. The list so far (in chronological order) is:

  • Cicindela (s. str.) tranquebarica kirbyi – ho hum, we’ll see this in several places.
  • Cicindela (s. str.) purpurea audubonii – über common Great Plains species, although the black form is always a treat to see.
  • Cicindela (s. str.) pulchra – YEAH! Seen in good numbers at one of the new South Dakota localities discovered in 2008 by Matt Brust (our personal chaperone for the day). Marvelous field photographs.
  • Cicindela (s. str.) fulgida – Only one seen, but Chris got a nice series of field photographs (I’ve seen good numbers of this species from my previous trips to this area in 2008 and in Oklahoma last year).
  • Cicindela (s. str.) nebraskana – Another “A list” species for the trip, but we’ve only seen one so far.
  • Cicindela (Cicindelidia) punctulata punctulata – also known as Cicindela ubiquita.
  • Cicindela (s. str.) scutellaris scutellaris – even though this is a common Great Plains species in any sandy area, I never tire of its dazzling red elytra and blue/green head and pronotum.
  • Cicindela (s. str.) lengi – The third species on our “A list” that we’ve seen, with some real nice field photographs from Monroe Canyon.
  • Cicindela (s. str.) formosa generosa – another common Great Plains species.
  • Cicindela (s. str.) denverensis – I didn’t expect to see this one on the trip (just a single individual at Monroe Canyon), but I’ll take it!

Tomorrow we’ll hit a Wyoming location where Cicindela (s. str.) decemnotata is known to hang out – a species I’ve not yet seen, either alive or preserved. Most sources regard this species as closely related to C. denverensis, but Matt thinks it is actually more closely related to C. fulgida due to similarity in form and shine but green instead of purple. Afterwards, in a major addition to our planned itinerary (hence the updated Google Map), we’ll go into northwestern Colorado to look for two very cool subspecies of the otherwise widespread species – C. formosa gibsoni and C. scutellaris yampae. If we’re lucky we’ll also see the delicate little sand lover, Cicindela (s. str.) limbata, but if we don’t see it there then we should see it the next day when we finish out the trip back in the Nebraska Sand Hills just east of Alliance. But before that, we’ll veer back up into Wyoming and look around in the high elevations east of Laramie in hopes of finding Cicindela (s. str.) longilabris laurentii. That one may be a stretch, but if we are successful then we have the potential to see a total of 15 species – that would be a trip high for me (literally and figuratively).

Copyright © Ted C. MacRae 2010

The last survivor

/ Ted C. MacRae / 8 Comments

This past June I made two trips to the Loess Hills of extreme northwestern Missouri as part of a follow-up survey for Cylindera celeripes (swift tiger beetle).¹ I was hoping to identify additional populations, however small, of this tiny, flightless, enigmatic species to go along with the three that colleague Chris Brown and I discovered last year.  The results were good news, bad news – no new populations were found, but I was able to re-confirm the beetle’s occurrence at two of the sites where we found the beetle last year.

¹ Some of you may recall my excitement at finally finding this long-sought after species in Missouri – apparently limited to the state’s few remaining high quality loess hilltop prairie remnants.

One of the sites that I had hoped might harbor the beetle is Squaw Creek National Wildlife Refuge in Holt Co. – located very near McCormack Loess Mounds Natural Area where the beetle was seen both this year and last.  Squaw Creek features several thousand acres of restored wetland habitat in the Missouri River valley that serve as resting, feeding, and breeding grounds for migratory birds and other wildlife.  Located within the Mississippi Flyway, the refuge is best known for its large concentrations of snow geese and bald eagles.  Wetlands are not good habitat for C. celeripes, but it was not the wetlands I was interested in visiting (well, I am really interested in visiting the wetlands someday – but on these visits I had other goals).  Rather, it was the tiny slivers of loess hilltop prairie that still remain on the fingers of loess bluffs along the eastern boundary of the refuge.  Twice scouring these prairie remnants over a two-week period failed to reveal the presence of the beetle, but on the first visit I did see this lone, rather ragged-looking adult male Cicindela limbalis (common claybank tiger beetle).  Unlike the aforementioned species, C. limbalis is rather common throughout most parts of the state on upland clay exposures. A spring-fall species, adults first emerge in September, have a little fun (which includes feeding but not mating), and then dig back into the ground for the winter before emerging once again in the spring. It is one of the first insects to greet the new season (I’ve seen them as early as late March) – mating and oviposition occur over the next month or two, and by end of May these guys are pretty well spent.  An interesting feature of the populations found in extreme northern Missouri is their higher degree of elytral maculation.  Compare this relatively fully-marked individual with this female that I reared from a larva collected at Knob Noster State Park in west-central Missouri (incidentally, my first ever reared tiger beetle!).

This male is clearly among the last of his generation in this area – not only did I not see any other individuals on the entire trip, but he clearly exhibits signs of wear and tear.  I found him nibbling on this dead millipede (which larger tiger beetles are known to prey upon); however, I don’t think this guy actually killed the millipede.  Rather, I think he found it already dead and was scavenging one of the only meals still available to him.  Closer examination of the face reveals that his left mandible is broken off near the base (best seen in the enlarged photo) – whether a result of battle with over-sized prey or a narrow escape from predation himself is hard to say.  Regardless, with only one “tooth” his ability to capture prey on his own has been severely compromised, and about all he can do is look for already dead prey items on which he can scavenge.  As one of the last survivors of his class, one can only hope that he lived a long and fruitful life, killed much prey, and inseminated many females.

Photo Details: Canon 50D w/ 100mm macro lens (ISO 100, 1/250 sec, f/14-16), Canon MT-24EX flash (1/4 ratio) w/ Sto-Fen diffusers. Typical post-processing (levels, minor cropping, unsharp mask).

Copyright © Ted C. MacRae 2010

…the “better” Eleodes suturalis

/ Ted C. MacRae / 8 Comments

As I mentioned in my previous post, I really wasn’t satisfied with the photographs I took of the clown beetle, Eleodes suturalis, that I brought back from Oklahoma. I had placed the beetle in a terrarium of native soil and taken the obligatory whole beetle and head close-up photographs, both showing all the characters needed to identify the species in adequate detail. They were good, scientific photos, but they weren’t very exciting. In fact – they were boring! Now, I know not every subject I photograph is going to be a wower (the giant desert centipede I recently featured probably setting that standard), but it is important to me that the photographs I post here at least be interesting. After taking those first E. suturalis photographs, then being underwhelmed as I brought them up one-by-one on the computer, I started thinking about whether certain insects are just ‘homely’, and no matter how you photograph them they will still be homely. Eleodes suturalis is by no means a homely beetle in real life, but that is due mostly to the impressiveness of its size – a quality not easy to project in photographs.  Beyond that, its somber coloration, lack of unusual morphological modifications, and “beady little eyes” (fide Adrian) don’t offer much else in the way of help.  Combine that with the unflattering salmon coloration of its native soil as a substrate and an exoskeleton just shiny enough to cause annoying specular highlights, and you’ve got a recipe for really boring beetle photographs!

That’s when it occurred to me to try photographing the beetle in a white box.  I’ve only just begun to experiment with this technique and have been impressed with its ability to make somber-colored subjects (e.g., Gromphadorina portentosa) attractive and truly beautiful subjects (e.g. Buprestis rufipes) simply stunning.  The sharp, clean environment of a white box demands a clean beetle, so I gave the beetle (who had done much digging since the previous photo shoot) a good soaking and scrubbing (to the beetle’s great disapproval!).  Yes, I know there is still some dirt on him, but I think a dental pick and wire brush would have been needed to remove every last bit, caked on as it was!  Despite that, I think I achieved the desired effect – specular highlights… gone!  Boring background… gone!  Clean and crisp and ready to impress! The photos also do a much better job of highlighting the 3-dimensionality of the beetle than the original photographs.  Of the many photos I took, my favorite is featured above, and below I present two more that closely approximate the vantage of the two photos I posted from the first shoot in a side-by-side comparison.

For those of you wondering how I managed to secure the beetle’s cooperation for these photos, I used a modification of the “lens cap” technique, covering the beetle with a large glass bowl instead.  The beetle crawled around under the bowl for a bit but eventually would end up settled down against the edge.  By carefully lifting the bowl I was able to avoid disturbing the beetle and fire a few shots before it would start wandering again.  I just repeated the process until I was satisfied I had a few good shots in the sequence.

Does this mean an end to my preference for in situ photographs?  Certainly not.  But some beetles just look better in white!

Photo Details:
White box: Canon 50D w/ 100mm macro lens (ISO 100, 1/250 sec, f/18-20), Canon MT-24EX flash, indirect. Typical post-processing (levels, minor cropping, unsharp mask).
Terrarium: same except f/18, direct flash w/ Sto-Fen diffusers.

Copyright © Ted C. MacRae 2010

The real Eleodes suturalis…

/ Ted C. MacRae / 3 Comments

I recently posted a photograph of a clown beetle (Eleodes hispilabris) (family Tenebrionidae) that I found last July in the Glass Mountains of northwestern Oklahoma.  I had encountered that individual while stumbling through the mixed-grass prairie in the middle of the night in search of the Great Plains giant tiger beetle (Amblycheila cylindriformis).  Although I eventually found the latter species, it took a few hours, during which time I was forced to examine numerous individuals of another clown beetle, Eleodes suturalis – perhaps the most conspicuously common clown beetle in the Great Plains.  I didn’t bother to take photographs of them, focused as I was on my tiger beetle search and owing to the fact that this was not the first time I’d encountered that species in abundance (the first time being many, many years ago as they crossed the highway en masse just a few miles north of the Glass Mountains in Barber Co. Kansas).  In fact, I was becoming rather annoyed with them due to their great similarity in size and coloration to the object of my desire¹, and only when I found the previously photographed individual doing the defensive “head stand” so characteristic of the group did I relent and break out the camera for a series of shots (not easy in the dark of night).

¹ Wrigley (2008) even suggested a mimetic association for Amblycheila cylindriformis and Eleodes suturalis due to their similarity in size, shape and coloration (black with a reddish-brown sutural stripe).

Of course, that individual turned out not to be E. suturalis, but the closely related species E. hispilabris, a fact that I did not realize until several days later as I was examining the photographs more closely. Fortunately, I happened to bring home with me a live individual of what truly represents E. suturalis, which I show in these photographs.  I’m not sure exactly why I brought a live one home with me – I’ve done more and more of this in recent years, mostly just to observe them and see what they do.²  I think in this case, I was intrigued by the possible mimetic association between this species and A. cylindriformis and wanted an individual for comparison with the several live A. cylindriformis individuals that I also brought back with me.

² The singular focus on collecting “specimens” that I had during my younger years seems to be giving way to a desire to know more about species as living entities and not just their external morphology.

Unlike E. hispilabris (my identification of which I only consider tentative), there can be little doubt that the individual in these photographs represents E. suturalis.  No other clown beetle in the Great Plains exhibits the sharply laterally carinate elytra and broadly explanate (spread outward flatly) pronotum (Bernett 2008).  The reddish-brown sutural stripe of the distinctly flattened elytra is also commonly seen in this species, although occasional individuals of a few other clown beetle species exhibit the stripe as well (including E. hispilabris, which likely was the reason I assumed it represented E. suturalis).  All of the characters mentioned above can be seen in the photographs shown here.  However, I nevertheless find the photos rather unsatisfying.  If you think you know why, feel free to comment, otherwise you can wait for the “better” photos…

Photo Details: Canon 50D w/ 100mm macro lens (ISO 100, 1/250 sec, f/18), Canon MT-24EX flash w/ Sto-Fen diffusers. Typical post-processing (levels, minor cropping, unsharp mask).

REFERENCES:

Bernett, A. 2008. The genus Eleodes Eschscholtz (Coleoptera: Tenebrionidae) of eastern Colorado. Journal of the Kansas Entomological Society 81(4):377–391.

Wrigley, R. A.  2008. Insect collecting in Mid-western USA, July 2007.  The Entomological Society of Manitoba Newsletter 35(2):5–9.

Copyright © Ted C. MacRae 2010

Rearing the Prairie Tiger Beetle (Cicindela obsoleta vulturina)

/ Ted C. MacRae / 12 Comments

A Prairie Tiger Beetle larva peers up from its burrow in rocky soil of a dolomite glade in the White River Hills of southwestern Missouri. The head of this 3rd-instar larvae is about the size of a pencil eraser.

I had so looked forward to the long Memorial Day weekend collecting trip – time of season and the weather were perfect, and it had been several years since I’d made a late spring swing through the woodlands, glades, and prairies of western Missouri. But after two fruitless days of searching for nearly non-existent beetles at Ha Ha Tonka State Park, Lichen Glade Natural Area, and Penn-Sylvania Prairie, I was faced with a choice: return home disappointed or try something completely different in an attempt to salvage the weekend.  I chose the latter.

A 3rd-instar Prairie Tiger Beetle larva extracted from its burrow. Total length is ~30mm.

What could be more different than the White River Hills of southwestern Missouri?  The deeply dissected dolomite bedrocks supporting xeric, calcareous glades, dry woodlands and riparian watercourses couldn’t be more different than the gentle, acidic sandstone terrain of those more northerly locations.  Its hilltop glades (“balds”) are the most extensive such system in Missouri, and I’ve already featured several charismatic insects from my travels last summer to this part of Missouri, including Megaphasma denticrus (North America’s longest insect), Microstylus morosum (North America’s largest robber fly), and Plinthocoelium suaveolens (North America’s most beautiful longhorned beetle).  One insect that I also wanted to feature from that area but that eluded me during last fall’s cold and wet collecting trip is the Prairie Tiger Beetle – Cicindela obsoleta vulturina.  This impressive species is highly localized in Missouri, occurring no further north and east than the White River Hills.  Moreover, the populations in this part of the state and across the border in Arkansas are highly disjunct from the species’ main population in the southern Great Plains.  Like a number of other plants and animals, the Missouri/Arkansas disjunct may represent a relict from the hypsithermal maximum of several thousand years ago, finding refuge in these rocky hills after cooling temperatures and increasing moisture caused the grasslands of today’s west to retreat from their former eastern extent.

The ''business end'' - four eyes and two enormous mandibles. The metallic purple pronotum is covered with soil.

Despite its restricted occurrence in Missouri, the species is apparently secure and occurs commonly on the many dolomite glades that are found in the area. I have records from a number of localities in the White River Hills, but the best populations I’ve seen occur at Blackjack Knob in Taney County.  Of course, I would have absolutely no chance of seeing the adults during this Memorial Day weekend – adults don’t come out until late summer rains trigger emergence in late August and early September.  It was not, however, the adults that I was after, for I had seen larvae of what I believed must be this species in their burrows during one of my visits to this location last summer.  Although I have collected several other species of tiger beetles in the area, I reasoned these larvae must represent C. obsoleta vulturina due to their rather large size (this species is one of the largest in the genus in North America) and because they lacked the white bordering of the pronotum typical of species in the genus Tetracha – the only other genus occurring in Missouri with species as large as this.  I had tried to extract some of the larvae for an attempt at rearing, but neither of the two techniques I tried (“fishing” and “jabbing”) had worked.  Fishing involves inserting a thin grass stem into the burrow and yanking out the larva when it bites the stem; however, I found the burrows of this species to angle and turn due to the rocky soil rather than go straight down for a clear shot.  Jabbing involves placing the tip of a knife at a 45° angle about 1″ from the edge of an active burrow, waiting for the larva to return to the top of the burrow, and jabbing the knife into the soil to block the larva’s retreat – a quick flip of the knife exposes the larvae, but in this case jabbing did not work because I always ended up hitting a rock and missing the larva before it ducked back down in the burrow.

Hooks on the abdominal hump of a 3rd-instar Prairie Tiger Beetle larva prevent it from being pulled out of its burrow by struggling prey.

I returned to the site where I had seen larval burrows last year and once again found them.  I tried fishing a few, though I knew this would be futile, then jabbing – again with no success, and then had an idea.  I went to the truck and retrieved a small trowel that I use to dig soil for filling rearing containers, then found an active burrow (larva sitting at the top, though dropping upon my approach) and got in position using the trowel as I would the knife.  I held the trowel firmly with both hands and placed my body behind it so I could use all my weight to force the trowel into the soil and past the rocks when the larva returned to the top of the burrow – worked like a charm!  After taking photographs of the first larva that I successfully extracted, I set to the business of collecting nearly a dozen more over the next couple of hours.  I then filled several containers with soil (using rocks in the larger one to create “compartments” to keep the larvae separated), poked “starter burrows” in the soil, and one at a time placed the extracted larvae in the burrows and sealed them in by pushing/sliding my finger over the hole.  I’ve found this is necessary to prevent the larvae from crawling right back out and digging a new burrow somewhere else – not a problem if there is only one larva in the container (although I prefer they use the starter burrows that I place at the edge of the container so that I can see them in their burrows to help keep track of what they are doing); however, in containers with more than one larva they will often encounter each other and fight, resulting in some mortality.  Larvae sealed in starter burrows eventually dig it open again but generally continue excavating it for their new burrow.  One larva was not placed in a rearing container – it was kept in a vial for the trip home, where it was dispatched and preserved in alcohol as a larval voucher specimen.

This male adult Prairie Tiger Beetle (emerged 10 weeks after collecting the larva) shows the dark olive-green coloration and semi-complete markings typical of the MO/AR disjunct population.

After returning to St. Louis, I placed the rearing containers in a growth chamber and monitored larval activity 2-3 times per week.  Whenever a burrow was opened, I would place a fall armyworm, corn earworm, or tobacco hornworm larva in the burrow and seal it shut.  Some burrows would be re-opened almost immediately and, thus, fed again, while others stayed sealed for longer periods of time.  Tap water was added to the container whenever the soil surface became quite dry – generally once per week, and by late July nearly all of the burrows were sealed and inactive. If these larvae did, indeed, represent C. obsoleta vulturina, then this would be the time they would be pupating.  On August 15 I had my answer, when I checked the containers to find the above male had emerged, and the next day two more adults emerged as well (including the female shown below).

This female adult Prairie Tiger Beetle emerged the same day as the male and shows slightly brighter green coloration.

I put the emerged adults together in the largest rearing container, and within minutes the male and one of the females were coupled. I’ve kept them fed with small caterpillars and rootworm larvae, and numerous oviposition holes were eventually observed on the surface of the soil in the container. In a few weeks, I’ll place this container in a cold incubator for the winter and then watch next spring to see if larvae hatch and begin forming burrows. If so, it will be a chance to see if I can rear the species completely from egg to adult and preserve examples of the younger larval instars.

Photo Details: Canon 50D (ISO 100, 1/250 sec) w/ Canon MT-24EX flash w/ Sto-Fen + GFPuffer diffusers. Typical post-processing (levels, minor cropping, unsharp mask).
Photos 1-2, 5-6: 100mm macro lens (f/14-f/16).
Photos 3-4: 65mm MP-E 1-5X macro lens (f/14).

Edit 9/10/10, 6:30 pm: I checked the terrarium today and discovered 24 brand new 1st-instar larval burrows dotting the soil surface.  They are quite large already, almost as big as 3rd-instar burrows of the diminutive Cylindera celeripes.  I guess I’m surprised to see larvae hatching already, as I expected they would overwinter as eggs and hatch in the spring.  Now that I think about it, however, hatching in the fall makes sense, as this gives them an opportunity to feed some before winter sets in and also allows them to burrow for more protection from freezing temperatures.  I’ve dumped a bunch of 2nd-3rd instar Lygus nymphs into the terrarium for their first meal.

Copyright © Ted C. MacRae 2010