Nebraska

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

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

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

ID Challenge #1

/ Ted C. MacRae / 28 Comments

Okay, this isn’t really the first ID challenge I’ve had on this site, but the first in a series that is formally named such.  I’ll be offering these up occasionally to fill the void left by the suspension of Alex’s Monday Night Mystery series (okay, not really a void – we still have a wealth of serial quizzes to choose from, including Crypsis Challenges by Troy, Monday Mimic by Mike,  by Chris, Genius of the Press by the other Chris, Electron Challenge by macromite, and my own !).  This series will feature classic identification challenges, with points awarded for correctly naming the order, family, genus, and species.  Points are not mutually exclusive – you don’t have to be first, you just have to be correct.  That being the case, I’ll turn on comment moderation during the answer phase so that all have equal opportunity to participate.  I also give bonus points for providing additional diagnostic information, comments on taxonomic status, or even wrong answers if they somehow make me chuckle.  I’ll give this a day or so – starting… right… now.

Update 12/24/10: answer posted here.

Copyright © Ted C. MacRae 2010

Cleaning Tiger Beetles

/ Ted C. MacRae / 22 Comments

Cicindela scutellaris scutellaris - the festive tiger beetle

This is Cicindela scutellaris (festive tiger beetle), one of the six species of tiger beetles that we found last September at Monroe Canyon in the Pine Ridge area of northwestern Nebraska.  The red elytra and green head and pronotum are characteristic of nominotypical populations of this species that are found in sandy habitats throughout the Great Plains.  This is your classic tiger beetle in a classic tiger beetle pose; however, photographs such as this are not so easy to come by.  The biggest challenge is the beetle itself – rarely are they so accommodating to allow this nice lateral profile perspective with the head slightly cocked towards the camera while standing up on their front legs.  This posture is seen only when the beetles are warm and active, and warm beetles are skittish beetles that yield lots of not-as-interesting back shots (head directed away from the camera) as they persistently run away from the photographer.  Cooler temperatures make them less skittish and easier to approach from the desired angle, but in this case they often lay flat on the ground trying to absorb heat – flay-laying beetles are not very photogenic either.  With practice and patience, one learns how to “work” an active, skittish subject and get them accustomed to the photographer so that the above perspective can be achieved.

Getting the shot, however, is only half the battle.  Tiger beetles are dirty bugs!  They run around over bare ground and dig in it, often leaving them covered with debris.  This is particularly true for species that frequent sandy habitats.  For those of us who like to photograph wild individuals in their native habitats, debris-covered beetles is something we have to live with.  Or do we…?  The beetle in the above image looks squeaky-clean thanks to some simple digital image processing tools that I used to “clean up” the subject (I use Photoshop Elements 6.0).  Now, I’ve never been one to want to spend a lot of time on post-processing of my photographs.  I’d rather be looking for bugs, photographing them, studying them, and writing about them – time spent on post-processing is time not spent on any of these other activities.  However, I have developed a little routine that I follow for most of my tiger beetle photographs now that cleans them up a bit – some more than others – and doesn’t take too much time.  Maybe some of you will find this useful for your own photographs.¹

¹ Disclaimer:  I am not a Photoshop expert.  I’m not even a photographer.  I’m an entomologist with a camera.  As a result, this post is intended to be not so much an authoritative tutorial on the use of Photoshop as a summary of what I’ve learned in dealing with my own photographs.  Constructive dialogue about these and other techniques is welcome. 

Like it or not, no digital image comes out of the camera ready to use (still perhaps the most perplexing aspect of this whole digital photography thing for me personally).  Almost every image needs some levels adjustment and unsharp mask applied to it, and while others are against it I’m not above doing a little cropping to enhance the final composition of the photograph (hey, it’s difficult enough just getting these guys in the frame, much less positioned exactly where you want them).  These are the basic steps that I follow for almost every photograph, as illustrated in the following sequence (reduced versions used for all photos):

Original photograph before processing.

Slight cropping to enhance composition.

Levels adjusted to brighten photo.

Unsharp mask applied (amount = 80%, radius = 2.0 pixels, threshold = 12 levels).

 Normally I would be done at this point, but there are two things that bother me about this photo: 1) the dark shadow on the distal back portion of the elytra (common with this pose), and 2) the debris scattered about on the eye, mandibles, thorax, and elytra.  To fix the shadow, I used the Magic Wand Tool (set on contiguous) to select the shadowed area of the elytra, then used the Dodge Tool set on Highlights (exposure = 25%) to lighten the shadowed area.  For the debris, I enlarged the photo to 100% and used the Spot Healing Brush Tool to remove most of the sand particles, adjusting the size of the brush to just larger than the size of the individual sand particles.  This works fine for particles surrounded by a uniform background, but it doesn’t work so well for particles along edges (particularly the mandibles).  For this, I used the Clone Stamp Tool (again, with the photograph enlarged to 100%) and carefully “cloned” a clean spot along the edge of the mandible next to the sand particle and then replaced the piece of debris with the cloned piece of the image.  As with the Spot Healing Brush Tool, the pixel size is set to the smallest size needed for the size of the debris particles.  Compare the above image with the finished image below to see the difference.

Finished photo with dark shadows on elytra and sand debris on body removed.

 The biggest improvements can be seen with the eyes, always the focal point of a photo such as this, and the mandibles – both now appearing nice and clean.  Is this cheating?  Have I compromised my ideal of getting an image of a wild individual of this species in its native habitat?  I’d be interested to know your opinion about this.

Photo Details: Canon 50D w/ 100mm macro lens (ISO 100, 1/250 sec, f/16), Canon MT-24EX flash w/ Sto-Fen + GFPuffer diffusers.

Copyright © Ted C. MacRae 2010

Monroe Canyon – A Tiger Beetle “Hot Spot”

/ Ted C. MacRae / 16 Comments

Steep, sparsely vegetated, fine sand road cut on the Nebraska Pine Ridge escarpment.

The vast landscape surrounding the Nebraska Pine Ridge boasts two entirely different natural communities – the High Plains shortgrass prairie atop the ridge stretching endlessly to the south, and the eerie, desolate Badlands on the north side of the ridge extending to the Black Hills of South Dakota.  Separating these two distinctive communities is the Pine Ridge escarpment itself – a precipitous 1,400-ft drop whose ponderosa pine forests and sage brushlands are more reminiscent of the Rocky Mountains some distance to the west rather than the Great Plains that surround them.  Instead of hard igneous and metamorphic rocks, however, the Pine Ridge is composed of soft, erodable sand- and siltstones, giving rise to canyons with dramatic white bluffs and escarpments.  One of the more scenic of these is Monroe Canyon, located six miles north of the tiny town of Harrison and part of the Gilbert-Baker State Wildlife Management Area.  I first explored Monroe Canyon two years ago, when Matt Brust took me there after our successful quest to see Cicindela nebraskana (prairie long-lipped tiger beetle) in the prairies above.  The steep, eroded road cuts in Monroe Canyon had become one of Matt’s favorite spots to look for tiger beetles, but on our visit there was not much going on save for single individuals of the ubiquitous sand-loving species Cicindela formosa (big sand tiger beetle) and Cicindela scutellaris (festive tiger beetle).  Still, the fine, deep, sparsely vegetated mixture of sand and silt extending far up the embankment is classic tiger beetle habitat, so when Chris Brown and I returned to the area this past September, we decided to give Monroe Canyon another try.

Of the several sand-associated tiger beetles that I thought we might encounter here, Cicindela lengi (blowout tiger beetle) was the one I was really hoping for.  I had encountered a few scarce individuals of this C. formosa-look alike during my 2008 trip and eventually reared another individual from suspected larvae plucked from their burrows.  My only photographs of this species, however, were taken during my PNS days, and I longed to see them once again through the viewfinder of a proper macro-rig.  The day hadn’t started well, getting skunked at a clay bank site in Crawford on the way to Monroe Canyon (where I resorted to photographing itty bitty little moths), and early indications once we got to Monroe Canyon were that it was going to be slow there as well.  Sporadic sightings of Cicindela purpurea audubonii (Audubon’s tiger beetle) had me yawning, and a lone individual of the remarkably infidel Cicindela ubiquita [= C. punctulata] (punctured tiger beetle) seen close to the roadside did little to boost my enthusiasm.  Still, conditions just seemed “right” and the habitat was extensive enough that it deserved a thorough searching before passing judgement.  I got a little more excited when I encountered a few C. purpurea audubonii black morphs, of which I got my first nice field photographs (you’ll see these in a future post), and then spent some time staking out larval burrows for attempted photographs.  We ended up spending a couple of hours at the site without seeing anything remarkable, but by then it was early afternoon and there was little point in trying to find another locality to search – it was a gorgeous spot on a gorgeous day, and just being out there was almost reward enough.  (I’m guessing by now you see where this is going…)

Cicindela lengi - blowout tiger beetle

As I began my umpteenth pass along the lower stretch of the embankment, I heard Chris call out, “I’ve got it!”  Chris hadn’t previously seen this species, so I fully expected when I walked over to where he was standing that I would find instead the much more common and amazingly similar C. formosa.  However, when I spotted the adult as he pointed to it, there was no doubt – the longer, obliquely straight humeral lunule (shoulder marking), the slightly more cylindrical, parallel-sided body, the more extensive brilliant green marginal highlights on the head and pronotum – it was, indeed, C. lengi!  The close resemblance of C. lengi to C. formosa is not the result of a close relationship, but rather an example of convergent evolution in response to similar habitat.  Cicindela lengi is actually more closely related to C. tranquebarica (oblique-lined tiger beetle) and other species formerly placed in the now defunct subgenus Tribonia.  As the first finder, Chris had first photo honors as well while I stood back, ready with the net should it spook and become uncooperative.  It did make a few short escape flights at first, but as I’ve learned before this species tends to make very short, weak flights before dropping straight down, making it rather easy to follow even on the steep embankment that we found ourselves.  This contrasts with C. formosa, whose long, powerful escape flights and bouncing tumbles upon landing can make them difficult to follow.  Eventually it became accustomed to our presence, and after Chris was satisfied with his photographs it was my turn.  We then we took turns again just to make sure we really got the shots we wanted.

Cicindela lengi - note the obliquely straight humeral lunule and relatively narrow, parallel-sided body.

It’s a good thing we didn’t pull the plug on Monroe Canyon that day, as tiger beetle activity really picked up during the afternoon hours.  Not only did we end up seeing several individuals of C. lengi during the next couple of hours, but also a few individuals of C. formosa and C. scutellaris and a single, seemingly misplaced Cicindela denverensis (green claybank tiger beetle), more fond of clay substrates than sand) – making Monroe Canyon a veritable “hot spot” of tiger beetle diversity.  While Monroe Canyon may not equal Willcox Playa, Laguna del Perro, Salt Plains National Wildlife Refuge, or Florida’s Road to Nowhere, six species is still a respectable amount of diversity by any measure, especially for a dry, upland site (all of the other sites mentioned are lowland saline habitats that owe their tiger beetle diversity at least in part to their broad range of available moisture zones).  After two days in the field, our trip total now stood at ten species, and in retrospect we were lucky to see C. lengi when we did as our subsequent search of the C. lengi spot 4 miles east of Harrison later that day turned up nothing.

Brilliant green highlights contrast spectacularly with the red body and bold white markings.

Copyright © Ted C. MacRae 2010

Tiny little slivers of life

/ Ted C. MacRae / 13 Comments

Day 1 of the 2010 Fall Tiger Beetle Trip™ had been an unqualified success.  Not only did we achieve our top goal of the trip – seeing good numbers of the recently discovered South Dakota population of Cicindela pulchra (beautiful tiger beetle), but we also saw C. nebraskana (prairie long-lipped tiger beetle) and a variety of other interesting insects in the nearby Nebraska Pine Ridge.  For Day 2, our destination was Monroe Canyon on the north face of the Pine Ridge escarpment, but on the way there we decided to check out some roadside clay banks in the town of Crawford.  Despite their appearance as perfect tiger beetle habitat, all we saw was a single individual of the normally ubiquitous C. purpurea audubonii (Audubon’s tiger beetle).  The area looked quite dry, and in fact there was little insect life of any kind present… or so I thought.  As I stood there looking out onto the embankment while deciding my next move, I glanced down at a nearby composit shrub with small yellow flowers.  These are often attractive to a variety of beetles (Crossidius longhorned beetles would be nice!), but I saw none.  I started to move on, but before I did I noticed some tiny little slivers of life moving about on the flowers.  Kneeling down to take a closer look, I saw that they were moths – in fact, they were some of the smallest moths that I had ever seen, and the shrub was covered with them.  Now, I may pride myself on my broad-based entomology knowledge, but when it comes to microlepidopterans there is a decided gap in that knowledge.  I really had no idea what they might be, but for some reason the combination of their unknown identity and tiny size became for me an irresistible photographic challenge (made truly challenging by the unrelenting prairie wind).  I’m fortunate that Chris also became distracted photographing something – any other collecting partner surely would have grown impatient waiting for me to finally be satisfied I’d gotten some good shots.

As far as I can tell, these moths represent something in the genus Scythris or perhaps Neoscythris.  These are the so-called flower moths, placed either in the family Scythrididae (Microleps.org and Moth Photographers Group) or subfamily Scythridinae of the Xylorictidae (BugGuide.net and Tree of Life).  According to Microleps.org, the life histories of relatively few scythridid species have been determined – the few that have showing a preference for feeding (usually internally, e.g., as leaf miners) on members of the Asteraceae.  There are images of several species of Scythrididae at the aforementioned sites; however, it’s a large group, and the individuals in these photos don’t appear to match any of the illustrated species.  Perhaps Chris Grinter or some other microlepidopterophile will chance upon this post and either confirm or further elucidate the identity of these individuals. 

Photo Details: Canon 50D w/ MP-E 65mm 1-5X macro lens (ISO 100, 1/250 sec, f/13), Canon MT-24EX flash w/ Sto-Fen + GFPuffer diffusers. Typical post-processing (levels, minor cropping, unsharp mask).

Copyright © Ted C. MacRae 2010

Kirby’s Tiger Beetle

/ Ted C. MacRae / 23 Comments

Dry alkaline creek in the Oglala National Grasslands, Sioux Co., Nebraska

At the northern edge of the Pine Ridge in northwestern Nebraska, the land drops precipitously from verdant High Plains to the eerie Badlands below.  The sterile landscape of eroded slopes and irregularly shaped landforms is at once beautiful and harsh.  Short grasses and silver sagebrush seem to be the only plants capable of living here, providing the meagerest of forage for the mule deer and pronghorn antelopes that dot the gently rolling hills.  Dissecting these arid grasslands are a series of seasonally dry alkaline creeks that support a number of tiger beetle species.  The most interesting of these is Cicindela fulgida fulgida (crimson saltflat tiger beetle), a beautifully colored little species that is restricted to wet, alkaline habitats.  It was this species that I and colleagues Chris Brown and Matt Brust wanted to see when we stopped by one such creek after finishing up at the C. pulchra site in South Dakota (and still recovering from “pulchra-fever”).

Cicindela tranquebarica kirbyi - Kirby's tiger beetle

I had been to this spot two years before and encountered a small number of C. fulgida along with much higher numbers of C. purpurea audubonii (Audubon’s tiger beetle) and C. tranquebarica kirbyi (Kirby’s tiger beetle).  Our luck wasn’t any better this time, and in fact we would encounter only a single C. fulgida that day.  This was Chris’ first opportunity to photograph this species, while I had already gotten some reasonably good field photos of the species during my 2009 visit to Salt Plains National Wildlife Refuge in northwestern Oklahoma.  As he photographed the individual, I continuing scanning the bright, alkaline barrens.  While I was not finding any C. fulgida, I was seeing a fair number of C. tranquebarica kirbyi, and it occurred to me that I still lacked good field photographs of this species.  I began stalking different individuals, but in the heat of the day I found it impossible to get close enough to any of them to attempt any shots.  It wasn’t until I encountered the individual shown above, apparently dragging something from its rear end, that I was able to close in for some shots.  A closer look revealed the individual to be a male who had somehow gotten his genital capsule pulled out of his abdomen.  Just the thought of how this might have happened makes me cringe.  At any rate, the individual exhibits the relatively broader white maculations that distinguish this Great Plains/Rocky Mountain subspecies from the more eastern nominotypical subspecies.

A newly emerged Kirby's tiger beetle sits at the entrance of his burrow.

As I continued scanning the soil, I noticed a number of larval burrows of what I took to be this species located up near the edge of the vegetated zone.  One burrow in particular caught my attention – partly because of its slightly larger size and irregular outline, but also because there appeared to be something sitting within it.  A closer look revealed an adult tiger beetle sitting just below the burrow entrance.  Cicindela tranquebarica is a so-called “spring-fall” species that emerges initially in the fall as a sexually immature adult before digging back in for the winter and re-emerging in spring for mating and oviposition.  I thus took this individual to be a newly emerged male that had not yet decided to leave its burrow and burst forth into a life of adulthood.  The opportunity couldn’t be passed up – I took a few photos of him sitting there, then switched out the 100mm lens for the 65mm 1-5X lens.  I had to get real close for this last shot, which caused him to retreat somewhat in his burrow.  However, a knife thrust into the burrow below him, followed by careful twisting until it touched his rear, caused him to return to the burrow entrance and once again pause before embracing his new world.

A male Kirby's tiger beetle prepares to leave his emergence burrow.

Copyright © Ted C. MacRae 2010