nature

Calm waters, frenzied beetles

/ Ted C. MacRae / 20 Comments

North Fork River - Ozark Co., Missouri

The North Fork River in south-central Missouri, like most Ozark rivers and streams, flows clear and cold over gravelled bottoms. Sustained year-round by the numerous seeps and springs that result from the region’s unique Karst geology, it meanders through a mix of forest and woodland alongside massive bluffs of half-a-billion-year-old dolomite. While small rapids can be found where gravel bars approach the bluffs, for the most part the shallow waters course lazily and idyllically south toward the White River in northern Arkansas.

Dineutus sp. (poss. discolor, per Brady Richards)

Lazy waters are the domain of whirligig beetles (family Gyrinidae).  We encountered this ‘raft’ of beetles in a sheltered pool near the shore of the North Fork River while hiking the Ozark Trail last October.  These frenzied little beetles live almost exclusively on the surface of the water, where they feed on organisms or scavenge debris in their famously and erratically conspicuous aggregations.  Such behavior might make them seem vulnerable to predation, but in actuality the reverse is true.  Beetles in rafts benefit from the increased number of eyes that can better scan the environment for potential threats than can individual beetles (Vulinec and Miller 1989), and the larger the raft the more efficiently this occurs.  There is also evidence that the appearance of the rafts themselves is a signal to warn potential predators (primarily fish) of the noxious chemicals produced in the beetles’ paired pygidial glands (Ivarsson et al. 1996), despite the decidedly non-aposematic coloration of the beetles themselves.

Photo Details: Canon 50D w/ 17-85mm zoom lens, natural light. Photo 1 – 17mm, ISO 100, 1/25 sec, f/5.6; photo 2 – 85mm, ISO 500, 1/160 sec, f/5.6. Typical post-processing (levels, minor cropping, unsharp mask).

REFERENCES:

Ivarsson, P., B.-I. Henrikson and J. A. E. Stenson.  1996.  Volatile substances in the pygidial secretion of gyrinid beetles (Coleoptera: Gyrinidae).  Chemoecology 7(4):191–193.

Vulinec, K. and M. C. Miller. 1989. Aggregation and Predator Avoidance in Whirligig Beetles (Coleoptera: Gyrinidae). Journal of the New York Entomological Society 97(4):438–447.

Copyright © Ted C. MacRae 2011

Diversity in Tiger Beetle Larval Burrows

/ Ted C. MacRae / 42 Comments

One of the fascinating aspects of tiger beetle study is their often high degree of fidelity for specific habitats.  Some species prefer wet habitats, while others frequent the drier uplands.  Some like sand while others need clay.  Differences in salinity, vegetational cover, and even slope dictate what species might be expected to occur in a given habitat, thus, the diversity of tiger beetle species one encounters is directly proportional to the diversity of habitats explored.  Unfortunately, tiger beetles can be rather ephemeral in their occurrence as adults.  Despite a life cycle that requires at least one year (and may take 2-3 years or even more), adults are often present for only for a few short weeks.  Even during the time that adults are present, they often hide if conditions aren’t right (too cold, too hot, too wet, too early, too late, etc., etc.  Add to that their marvelous evasive capabilities, and it’s a wonder I ever see or catch any at all!).  The study of tiger beetles is not, however, entirely dependent upon the adults.  The presence of larval burrows in an area is also useful information, and through understanding of the species that might occur in an area and their habitat preferences, it is possible to identify – at least tentatively – the species that might be living in them.

Cicindela lengi? (sandy tiger beetle) - Sioux Co., Nebraska

To the uninitiated, tiger beetle burrows might seem nothing more than a simple hole in the ground – anything could have made it.  However, with experience one becomes able to distinguish tiger beetle larval burrows almost instantly from burrows made by other ground-burrowing organisms.  The most common type of burrow is recognized by a combination of characters – almost perfectly circular except for a slight flattening on one side that gives the burrow a faint D-shape, and with the edge smoothly beveled.  This is your classic tiger beetle burrow and, for most U.S. species of Cicindela and related genera, averages ~5-6mm in diameter for 3rd instar larvae (tiger beetle burrows are most often observed at 3rd instar, since it is this final instar in which the larva spends the majority of its time and the burrow becomes most noticable).  The above burrow is one such burrow, found at Monroe Canyon in northwestern Nebraska last September.  While a number of species are known from the area, there are only a few that make their burrows in deep dry sands such as those that occur at this site.  We can eliminate Cicindela formosa (big sand tiger beetle) for reasons discussed below, and we can also dismiss Cicindela limbata (sand blow tiger beetle) because the habitat is not the barren, wind-shaped sand blow habitat that the species prefers.  This leaves two possibilities – Cicindela scutellaris (festive tiger beetle), a common and widespread inhabitant of sand habitats throughout the Great Plains, and Cicindela lengi (sandy tiger beetle), a much more localized resident of sand habitats with more western distribution.  The burrow likely represents the latter, since adults of this species have been found with greater frequency than C. scutellaris on the very fine-grained sands that occur in this part of Nebraska.  My confidence in this ID is bolstered by the fact that a larva I collected in the area from just such a burrow successfully finished its development and emerged a few months later as an adult C. lengi.

Cicindela pulchra pulchra (beautiful tiger beetle) - Fall River Co., South Dakota

Sometimes size alone is enough to indicate the species responsible for a burrow.  The above burrow was encountered last September in southwestern South Dakota on a clay/shale embankment in sage/shortgrass prairie.  A number of tiger beetle species fond of clay were observed at the site, including the two generalist species Cicindela tranquebarica (oblique-lined tiger beetle) and Cicindela purpurea audubonii (Audubon’s tiger beetle).  However, at ~8 mm in diameter the burrow is too large to have been made by either of these species.  The only tiger beetle in the area capable of making a burrow this size is Cicindela pulchra (beautiful tiger beetle), and in fact this burrow was found at one of several sites recently discovered by Matt Brust for this species in South Dakota.  Note again the classic shape – slightly flattened along the bottom side (the flattening accommodates the mandibles of the larval head – tiger beetle larvae always orient themselves in one position when sitting at the burrow entrance).

Cylindera celeripes (swift tiger beetle) - Woodward Co., Oklahoma

Just as large size was diagnostic for the previous burrow, the small size of the above burrow was also diagnostic.  This burrow, found at Alabaster Caverns in northwestern Oklahoma in October, 2009, measured only 3-4mm in diameter and can only have been made by Cylindera celeripes (swift tiger beetle).  This provisional ID was suggested by the fact that adults of the species had been observed abundantly in the lichen-encrusted clay exposures of this shortgrass prairie the previous June.  This photo, in fact, represents the first-ever discovery of the larval burrow of this species, and the identity of the species was confirmed when the larva collected from this and neighboring burrows and placed in rearing containers in the lab later emerged as adults.  I have found very similar-sized burrows in bottomland forest habitats in southeastern Missouri where the closely related species Cylindera cursitans has been seen.  The burrows are identical in size and shape, but the drastic difference in habitat is enough to distinguish the species that made them.

Cicindela formosa formosa (big sand tiger beetle) - Sioux Co., Nebraska

Not all tiger beetles utilize the simple hole-in-the-ground style of burrow, but rather incorporate some rather unique engineering features that make specific identification much easier.  This burrow can only be made by Cicindela formosa (big sand tiger beetle), a common resident of a variety of dry sand habitats throughout the Great Plains and eastern U.S.  The burrow entrance is on the large size for U.S. Cicindela (~6mm in diameter), and rather than opening flush on the ground it is directed horizontally and opens into a pit that is excavated to one side and underneath the burrow entrance.  No other U.S. tiger beetle makes a burrow quite like this (although I have noted Cicindela limbalis (common claybank tiger beetle) burrows on steep clay banks with a similar but much less distinct excavation on their lower side).  The pit apparently functions as a trap for potential prey, and since I have most often encountered burrows of this species in areas with some slope, I suspect the pit may help the larva capture its prey by preventing the prey from tumbling down the slope at the first sign of trouble.

Cicindela formosa 3rd instar larvae - Sioux Co., Nebraska

This is a different burrow by the same species, also at Monroe Canyon last September, that shows a 3rd instar larva sitting at the burrow entrance.  The sickle-shaped mandibles are resting against the slightly flattened lower edge of the burrow entrance, while the round pronotum fills the rest of the entrance profile.  The upper pair of eyes can be seen above the mandibles, but the lower pair (between the upper pair and the mandibles) are not visible in this photo due to the downward-facing angle of the burrow entrance.  I waited for quite some time with camera in position in hopes that I could photograph the larva, and when it did return to the burrow entrance I had time enough to fire off just a couple of shots before it retreated once again to safety in the depths of its burrow.

Cicindela fulgida fulgida (crimson salt flat tiger beetle) - Sioux Co., Nebraska

This unusual-looking burrow was found in a dry clay saline creek bed in the Badlands of northwestern Nebraska last September.  The turret structure is unique, but the nearly perfectly round and smoothly beveled burrow entrance identify it, nevertheless, as that of a tiger beetle larva.  These burrows can only be made by Cicindela fulgida (crimson salt flat tiger beetle).  There are several other saline-tolerant tiger beetles species in Nebraska, but most such as Ellipsoptera nevadica knausii (Knaus’ tiger beetle), Eunota togata (cloaked tiger beetle), and Habroscelimorpha circumpicta johnsonii (Johnson’s tiger beetle) require much more moisture than was found in this bone-dry creek bad.  I’ve found two other much more widely distributed clay-associated species – Cicindela tranquebarica and Cicindela purpurea audubonii – at this and other sites where I’ve seen C. fulgida; however, the larvae of those species do not utilize this unique turret-shaped structure for their burrows.  The turret is thought to have a cooling function for the larva during the heat of summer by raising it above the hottest layer of air against the white salt-encrusted ground and by aiding in the dissipation of heat from the larval burrow.  I wanted to photograph the larva sitting at the burrow entrance and spent quite a bit of time stalking out this and nearby burrows for a chance to do so.  Alas, however, on this day the larvae had greater patience than I!

Cicindela tranquebarica kirbyi (Kirby's tiger beetle) adult & larval burrows - Sioux Co., Nebraska

The above burrow entrances were photographed in September 2008 at the same dry saline creek bed in Sioux Co., Nebraska.  I mentioned above that Cicindela tranquebarica kirbyi and Cicindela purpurea audubonii both occurred commonly at this site along with Cicindela fulgida; however, these burrows likely represent the former.  That species seems to be found more consistently in high saline environments than the latter, which in this case probably have their larval burrows in the more normal clay soil further away from the creek bed.  During that 2008 trip, I did collect larvae from burrows like these in several similar, high saline habitats in Nebraska, South Dakota, and Oklahoma, and in each case adults of C. tranquebarica kirbyi were what emerged.  I have also reared this species from larvae collected on clay banks and wet sand habitats – in all cases, the burrows are a tad larger than those I have seen for other species in the genus that I have reared, such as Cicindela limbalis and Cicindela repanda (common shore tiger beetle) – logical since adults of C. tranquebarica tend to be a little more robust than these other species (but smaller than Cicindela pulchra and Cicindela obsoleta vulturina (prairie tiger beetle)).  In the above photo, I believe the the upper-right burrow is that of a larva, while the the lower-left one is that of an emerged adult – note the not-perfectly-circular opening and more ragged edge to the burrow.  In fact, the latter burrow looks very much like the adult emergence burrow that I saw at this very location last September, in which the still unemerged adult was seen sitting!  Granular chunks of soil can be seen scattered about the latter burrow, but I believe these were actually tossed by the larva rather than the adult as a result of burrow excavation – the amount of soil an adult would need to remove to re-open its burrow for emergence would probably be far less than what can be seen in this photo.  I did not search the surrounding grasslands for larval burrows, but if I had done so, it is likely that I would have found similar burrows that belonged to the larvae of Cicindela purpurea audubonii – the only other tiger beetle that we have seen in this inhospitable place!

Copyright © Ted C. MacRae 2011

Red-eyed Devil

/ Ted C. MacRae / 29 Comments

In June 1994, I made my first insect collecting trip to Big Bend National Park.  Both of my previous visits to Texas had been to the Lower Rio Grande Valley, so I was anxious to see what beetle treasures awaited me in this huge chunk of western Texas.  For three days I sampled the astounding diversity of beetles found in the park’s low desert scrub, oak/juniper woodlands, and high pine forests, and on the final day I decided to visit the sotol grasslands – a transitional habitat between the desert and woodlands in the Chisos Mountains foothills.  Sotol (Dasylirion wheeleri) is the host plant of jewel beetles in the genus Thrincopyge – exquisitely beautiful beetles of metallic blue or green and vivid yellow.  Larvae bore through the plant’s dried flower stalks, while adults wedge themselves in the base of this agave-like plant, hidden from view by the plant’s long, strap-like, saw-toothed leaves.  I had not yet seen these beetles for myself, so I began searching the through the plants – carefully prying apart the wicked leaves in hopes of seeing adults peering up from the base, and then using my foot-long forceps to extract them.  It’s a painful process, as no amount of care completely prevents the plant’s stout, recurved spines from impaling and ripping forearm flesh while trying to grab and pull out the beetles! 

While prying apart the leaves of one particular plant, I was startled by one of the most imposing-looking insects that I have ever seen as it jumped up on top of the foliage and assumed this decidedly aggressive posture.  Although I recognized it as some type of katydid, it was unlike any I’d seen before – large and robust, vivid green and yellow with flashing red eyes, its short spotted hind wings outstretched, spiny forelegs held high, and huge jaws spread wide open.  Her long dagger-like ovipositor only added to her impressiveness.  So spectacularly terrifying was its threat display that I couldn’t resist the opportunity to collect it for eventual mounting in life-like position.  I felt a little silly being scared of a katydid but nevertheless took great care to avoid getting my fingers anywhere near those jaws as I gingerly corraled it into a jar. 

Neobarrettia spinosa is also known as the greater arid-land katydid or spiny bush katydid, but I prefer the name that has been coined by some – “red-eyed devil”!  This species belongs to a small genus of primitive katydids largely restricted to northern Mexico, with only two species extending north into the south-central and southwestern U.S.  The black front edge of the pronotum and (in life) red eyes identify this individual as N. spinosa (N. victoria, also occurring in Texas, has the pronotal front edge green and the eyes pale).  Unlike most katydids, which have adopted omnivorous or hervivorous feeding habits, species of Neobarrettia and their subfamilial relatives are pure carnivores capable of capturing and consuming prey as large as themselves.  Its bulging eyes, elongate and heavily spined forelegs, and massively robust mandibles on a large head (presumably for enlarged mandibular musculature) clearly represent adaptations for predation (Cohn 1965).

The painting above from Cohn’s revision of the genus shows the true colors of a living female and its threat display.  I collected this specimen before the days of the internet or my own interest in photography, so I had nothing but my memory to guide me as I tried to recreate the threat display during mounting.  I got it mostly right but missed on a few details – the wings should have been placed more vertically, and the insect also rears back more on its hind legs to display the brightly colored cephalic portion of its abdominal venter.  I could try to relax and remount the specimen, but given its fragility and the fact that doing so would do little to make it any more imposing, I think the pose I have it in now is just fine.

This turned out to be a more difficult ID Challenge than I anticipated, but a record number of participants played along anyway.  Dave wins this challenge with 11 pts on the basis of a correct identification and entertaining logic to accompany it.  Ben Coulter was the only other person to correctly identify the genus and species, earning 9 pts for 2nd place, while BitB’s own James Trager and TGIQ share the final podium spot with 5 pts each.  Ben continues to dominate the overall competition with 32 pts now, but the battle for 2nd place has really heated up – Janet Creamer (14 pts) and TGIQ (13 pts) have the edge, but Dave (11 pts), James Trager (11 pts), and Christopher Taylor (10 pts) are all within easy striking distance.

REFERENCE:

Cohn, T. J. 1965. The arid-land katydids of the North American genus Neobarrettia (Orthoptera: Tettigoniidae): their systematics and a reconstruction of their history.  Miscellaneous Publications of the University of Michigan Museum of Zoology 126:1-179.

Copyright © Ted C. MacRae 2011

ID Challenge #2

/ Ted C. MacRae / 34 Comments

Here is another straight-up ID Challenge. Standard rules apply:

  • Points awarded for correctly naming the order, family, genus, and species (2 pts each).
  • Bonus points may be given (at my discretion) for providing additional relevant information (e.g., diagnostic characters, biological/ecological uniquities, clever jokes, etc.).¹
  • Comments will be moderated during the 1- to 2-day open challenge period to allow all a chance to participate (you don’t have to be first to win!).
  • Submitted answers will be posted at the end of the challenge period along with the number of points earned.

¹ Don’t ignore the opportunity for bonus points – they often determine the winner in these challenges!

Good luck!

Copyright © Ted C. MacRae 2011

Monroe Canyon epilogue – Audubon’s tiger beetle

/ Ted C. MacRae / 20 Comments

Cicindela purpurea audubonii (Audubon's tiger beetle) - green morph

In my first post about Monroe Canyon in the Pine Ridge of northwestern Nebraska, I featured the sumptuous Cicindela lengi (blowout tiger beetle) – a target species for the trip and one of six tiger beetle species that Chris Brown and I would find at this quarter-mile long sandy roadside embankment.  Another species we found there was C. denverensis (green claybank tiger beetle), unexpected given its preference for clay soils, but like C. lengi also a target species and thus a welcome find.  We also saw some more common species – the nominotypical forms of C. formosa (big sand tiger beetle) and C. scutellaris (festive tiger beetle), both reliable residents of sand habitats throughout the Great Plains, as well as a few individuals of the often ubiquitous C. punctulata (punctured tiger beetle).  The most numerous of all, however, was C. purpurea audubonii (Audubon’s tiger beetle).  Despite being uncommon in other parts of its range (in fact, nominotypical populations are feared extirpated in some parts of the eastern U.S.), C. purpurea audubonii is one of the most commonly encountered tiger beetles in grassland habitats throughout the central Great Plains and Rocky Mountains.  This species belongs to a complex of several that are generally green in color and fond of clay soil habitats, such as C. denverensis, C. decemnotata (badlands tiger beetle), C. limbalis (common claybank tiger beetle), and C. splendida (splendid tiger beetle).  All of these species can co-occur with C. purpurea audubonii in the Great Plains, but the latter is distinguished by its faint purple tinge and distinct metallic purple border around the edge of the elytra and its reduced elytral markings consisting of a short, oblique middle line and a white rear tip at the edge of the elytra (Pearson et al. 2006).  All of these characters can be seen easily in classic pose in the above photograph.

Cicindela purpurea audubonii (Audubon's tiger beetle) - black morph

Despite its commonness, however, I actually did look forward to seeing this species – the reason being the occurrence of occasional all-black individuals in the population.  Tiger beetles as a whole are a variable lot – polytopism (geographically based variability) is the rule!  Despite this, for the most part individuals within a given population usually exhibit a fairly uniform appearance.  Occasionally, populations of some species – generally those at intergrade zones where different subspecies meet – will show variation on a continuum between two extremes.  The occurrence of two distinct morphs within a population, however, is rather unusual.  I lacked good field photographs of the all-black morph of C. purpurea audubonii (and also the green morph, for that matter), so I was pleased to encounter several individuals of the black morph while we were at Monroe Canyon.  As can be seen in the above photograph, black morph individuals are truly all-black, perhaps with a purple reflection but without a trace of green anywhere on the body.  They do retain the same pattern of reduced white markings exhibited by the green morphs.  As a result, these individuals can be confused with some other black species that also occur in the Great Plains, such as C. nebraskana (prairie long-lipped tiger beetle) and, at higher elevations, C. longilabris (boreal long-lipped tiger beetle).  These latter species were also targets for our trip, so we had to pay close attention to any black morphs that we saw to confirm their identity (C. purpurea audubonii black morphs are distinguished by their distinctly hairy frons).

Chris Brown waits patiently to photograph a burrowing wolf spider at the entrance of its burrow.

I’ve not been able to find any additional information about these black morph individuals and the possible causes for their occurrence.  Cicindela purpurea is a so-called “spring-fall” species, emerging in the fall as sexually immature adults and then spending the winter in burrows before re-emerging in the spring to mate and lay eggs.  As spring-fall species go, it is one of the earliest to appear in the spring and last to disappear in the fall.¹  This immediately brings to my mind a possible thermoregulatory function.  Low temperatures may be a challenge for the adults during early spring and late fall, and the black coloration could be an adaptation to maximize absorption of solar radiation for heat gain. This idea seems to be supported by the fact that the incidence of black morphs is greater at more northern latitudes and in the higher elevations of the western part of the subspecies’ range (as much as 20-40%), where overall lower temperatures would be expected to occur.

¹ Karl Werner even amusingly stated that this species “rather delights in chilly weather” (Acorn 2001).

REFERENCES:

Acorn, J.  2001. Tiger Beetles of Alberta: Killers on the Clay, Stalkers on the Sand. The University of Alberta Press, Edmonton, xix + 120 pp.

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 2011

BitB Top 10 of 2010

/ Ted C. MacRae / 38 Comments

Welcome to the 3rd Annual BitB Top 10, where I pick my 10 (more or less) favorite photographs of the year.  My goal for 2010 was to continue the progress that I began the previous year in my quest to become a bona fide insect macrophotographer.  I’m not in the big leagues yet, but I have gotten more comfortable with using my equipment for in situ field photographs and am gaining a better understanding of lighting and the use of flash.  I also began experimenting with different lighting techniques (e.g. white box) and diffusers and am putting more effort into post-processing techniques to enhance the final appearance of my photographs.  I invite you to judge for yourself how successful I’ve been toward those goals by comparing the following selections with those from 2009 and 2008 – constructive feedback is always welcome:

Best Tiger Beetle

Cicindela denverensis - green claybank tiger beetle

From ID Challenge #1 (posted December 23).  With numerous species photographed during the year and several of these dramatic “face on” shots, this was a hard choice.  I chose this one because of the metallic colors, good focus throughout the face, and evenly blurred “halo” of hair in a relatively uncluttered background.

Best Jewel Beetle

Buprestis rufipes - red-legged buprestis

From Special Delivery (posted July 13).  I didn’t have that many jewel beetles photos to choose from, but this one would have risen to the top no matter how many others I had.  The use of a white box shows off the brilliant (and difficult-to-photograph) metallic colors well, and I like the animated look of the slightly cocked head.

Best Longhorned Beetle

Desmocerus palliatus - elderberry borer

From Desmocerus palliatus – elderberry borer (posted November 18).  I like the mix of colors in this photograph, and even though it’s a straight dorsal view from the top, the partial dark background adds depth to the photo to prevent it from looking “flat.”

Best “Other” Beetle

Enoclerus ichneumoneus - orange-banded checkered beetle

From Orange-banded checkered beetle (posted April 22).  The even gray background compliments the colors of the beetle and highlights its fuzziness.  It was achieved entirely by accident – the trunk of the large, downed hickory tree on which I found this beetle happened to be a couple of feet behind the twig on which it was resting.

Best Non-Beetle Insect

Euhagenia nebraskae - a clearwing moth

From Euhagena nebraskae… again (posted October 21).  I photographed this species once before, but those photos failed to capture the boldness of color and detail of the scales that can be seen in this photo.

Best “Posed” Insect

Lucanus elaphus - giant stag beetle

From North America’s largest stag beetle (posted December 30).  I’ve just started experimenting with photographing posed, preserved specimens, and in fact this male giant stag beetle represents only my second attempt.  It’s hard to imagine, however, a more perfect subject than this impressively stunning species.

Best Non-Insect Arthropod

Scolopendra heros - giant desert centipede

From North America’s largest centipede (posted September 7).  Centipedes are notoriously difficult to photograph due to their elongate, narrow form and highly active manner.  The use of a glass bowl and white box allowed me to capture this nicely composed image of North America’s most spectacular centipede species.

Best Wildflower

Hamamelis vernalis - Ozark witch hazel

From Friday Flower – Ozark Witch Hazel (posted March 26).  The bizarre form and striking contrast of colors with the dark background make this my favorite wildflower photograph for the year.

Best Non-Arthropod

Terrapene carolina triunguis - three-toed box turtle

From Eye of the Turtle (posted December 10).  I had a hard time deciding on this category, but the striking red eye in an otherwise elegantly simple photograph won me over.  It was also one of two BitB posts featured this past year on Freshly Pressed.

Best “Super Macro”

Phidippus apacheanus - a jumping spider

From Jeepers Creepers, where’d ya get those multilayered retinae? (posted October 5).  I’m not anywhere close to Thomas Shahan (yet!), but this super close-up of the diminutive and delightfully colored Phidippus apacheanus is my best jumping spider attempt to date.  A new diffuser system and increasing comfort with using the MP-E lens in the field at higher magnification levels should allow even better photos this coming season.

Copyright © Ted C. MacRae 2011

Cicindela denverensis – green claybank tiger beetle

/ Ted C. MacRae / 8 Comments

Cicindela denverensis (green claybank tiger beetle) | Sioux Co., Nebraska.

Here are a few more photographs of the insect featured in ID Challenge #1, which is, in fact, Cicindela denverensis (green claybank tiger beetle).  Nearly every commentor got the first 6 points easy enough (2 pts each for order, family, and genus), but only Ben Coulter correctly identified the species.  A bonus point for proper italicization of the binomen (and a favorable ruling on a technicality) gave him 9 points and the win.  Second place goes to TGIQ, who smartly picked up bonuses to earn 8 points and edge the pack.  Charley Eiseman, Christopher Taylor, Delbert La Rue, jason, and Techuser crowd the final podium spot with 7 points each.

Distinguished by its green color, hairy frons, reduced maculations, and grassland occurrence.

Cicindela denverensis occurs in short- and mixed-grass prairie habitats in the central and western Great Plains, especially sites with clay soils.  It can be distinguished from a number of similar-looking species by its uniformly green color, hairy frons, often reduced maculations, and occurrence in grassland habitats.  Cicindela sexguttata is also uniformly green, but the frons in that species is glabrous, and it occurs further east in woodland habitats.  Cicindela decemnotata is also similar, but it usually has broad maculations and a shinier, oily appearance – often with some degree of red tinting.  Some subspecies of C. scutellaris are also green, but only rugifrons bears maculations and can be distinguished by it’s stockier form and Atlantic Coastal Plain distribution. Cicindela denverensis is actually most closely related to C. purpurea (cowpath tiger beetle), C. limbalis (common claybank tiger beetle), and C. splendida (splendid tiger beetle) – especially the latter two.  All three of these species exhibit some degree of purple or red on the pronotum, elytra, and/or legs that distinguish them from C. denverensis in most parts of their range.   There is, in fact, some disagreement about whether C. denverensis, C. limbalis, and C. splendida even represent distinct species, all of which demonstrate a similar preference for clay substrates but segregate into three partially allopatric populations – northern C. limbalis, southern C. splendida, and western C. denverensis.  Hybrid individuals can be encountered in areas where their distributions overlap, and this is especially so in central Nebraska – one of just a few spots where all three species occur together.  Schincariol & Freytag (1991) conceded a close relationship between the three based on morphometric analysis but still considered them distinct based on differences in elytral color, pattern, and percentage maculation and the number of non-sensory setae.  However, a recent phylogenetic analysis based on mitochrondrial DNA sequences strongly supports a single species hypothesis (Woodcock & Knisley 2009).  From an academic perspective, more thorough systematic analyses of the claybank group of tiger beetles would be of great interest (although I suspect many cicindelophiles with strictly philatelic interests will not be happy to see three species sunk into one).

Ponderosa pine mingles with prairie grasses on the Nebraska Pine Ridge escarpment.

The individual in the above photos was found at Monroe Canyon in the Pine Ridge escarpment of western Nebraska (Sioux Co.).  It was the only individual of this species that we saw there and was a bit of a surprise finding because of the generally sandy soils that characterize the spot – perhaps it was a vagrant individual that had found its way into the canyon from the more clay-based shortgrass prairie above.  We’ve seen greater numbers of this species further east in central Nebraska (Sherman Co.) along vertical roadside clay banks. The photograph below is one of those individuals and exhibits somewhat more complete maculations.  Note the sharp bend, or “knee,” on the median maculation that allows the species to be differentiated from C. limbalis (all-green forms of this species can be found at the northern limit of distribution for C. denverensis in North Dakota).  This individual also displays something else of interest – anybody?

Individual with more complete maculations | Sherman Co., Nebraska.

REFERENCES:

Schincariol, L. A. and R. Freitag. 1991. Biological character analysis, classification, and history of the North American Cicindela splendida Hentz group taxa (Coleoptera: Cicindelidae). The Canadian Entomologist 123(6):1327-1353.

Woodcock, R. M. and C. B. Knisley. 2009. Genetic analysis of an unusual population of the problematic tiger beetle group, Cicindela spendida/C. limbalis, from Virginia, USA (Coleoptera: Cicindelidae) using mtDNA. Entomological News 120(4):341-348.

Copyright © Ted C. MacRae 2010

ESA in absentia

/ Ted C. MacRae / 6 Comments

Click on image to see larger version.

The Entomological Society of America (ESA) held its 58th Annual Meeting earlier this week in San Diego, California. For those of you who were unable to attend, I’ve included a link to a poster that I and coauthors Chris Brown and Kent Fothergill presented, titled Cylindera cursitans: Distribution and Seasonal Occurrence in Southeast Missouri. Okay, I can already see the puzzled faces, as many of you know I was unable to attend myself. In fact, none of the poster authors were in attendance – if Kelly Tindall, Kent’s entomologist-wife, hadn’t attended the meetings the poster would have never seen the light of day.

Despite lead authorship on the poster, I had a minimal role in its preparation.  Kent did much of the dirty work – clipping text and figures from a manuscript on the subject that we recently submitted to the journal CICINDELA, while Chris and I sat back and gave thumbs up and thumbs down opinions on each iteration of Kent’s hard work.  My heartiest congratulations to Kent for producing such a nice piece of work, to both Kent and Chris for putting up with my obsessive nitpicking over every trifling detail as we readied the manuscript for submission, and to Kelly for lugging a poster halfway across the country in the middle of winter when it didn’t even have her name on it.

REFERENCE:

MacRae, T. C., C. R. Brown, and K. Fothergill.  2010. Cylindera cursitans: Distribution and Seasonal Occurrence in Southeast Missouri. Annual Meeting of the Entomological Society of America, San Diego, California, December 12-15, 2010.

Copyright © Ted C. MacRae 2010