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

North America’s largest stag beetle

/ Ted C. MacRae / 30 Comments

 

Here is the full-sized photo that provided the image for yesterday’s Super Crop Challenge #3.  The insect in the photo is, of course, a fine example of a male Lucanus elaphus – the giant stag beetle (family Lucanidae).  This striking insect is easily among North America’s most distinctive and recognizable species by virtue of the enormously super-sized mandibles sported by the males.  Its fearsome appearance belies the true nature of this harmless beetle, which spends its days feeding on sap that flows from wounds on the trunks and roots of trees.  Males use their massive mandibles in combat with other males, not for “biting,” but rather as tools to pry and lift their adversaries before dropping them to the ground.  Some marvelous photos of this behavior in a related European species can be seen at Stag Beetles Lucanus cervus Mating Behaviour.

I collected this specimen many years ago at an ultraviolet light (“blacklight”) that I had setup in the pine/oak forests at Pinewoods Lake, Carter Co., in the southeastern Ozarks – one of my favorite 1980’s beetle collecting spots.  This was in my early days of studying beetles, during which time I was actively collecting material as part of my statewide surveys for the families Buprestidae (MacRae 1991) and Cerambycidae (MacRae 1994).  Lucanus elaphus is not a commonly encountered species, especially in the western reaches of its distribution here in Missouri, and I’ll never forget my rabid excitement when I encountered this fine major male at my blacklight sheet.  For many years afterward it remained the only individual that I had ever encountered, until a few years ago when I came across a group of two males and one female feeding on a sap flow in a wet bottomland forest along the Mississippi River in the lowlands of southeastern Missouri.  I encountered another male the following year at a nearby location “rafting” on debris in floodwaters from the nearby river, and two weeks later at that same site I picked up several males and females in a fermenting bait trap.¹  Like most “uncommon” species with broad distribution across the eastern U.S., I suspect that its apparent rarity is an artifact due to habits that make it infrequently encountered rather than being truely scarce.

¹ I have used fermenting bait traps to collect a wide variety of beetles, but especially longhorned beetles.  My recipe is based on that described by Champlain and Knull (1932) – bring 12 oz. dark molasses and 12 oz. beer up to 1 gal. with water, mix well and add a packet of dry baker’s yeast to get the fermentation started.  Hang a 1/2-gallon milk jug with big holes cut in the sides in a tree along the edge of a woods and add ~1 quart of fresh liquid.  It generally takes 2-3 days for the liquid to really start fermenting and become attractive, and it will remain so for about another week or so.  Check traps every 2-3 days by pouring the liquid through a kitchen strainer into another container – reuse or replace as necesssary. Place the collected specimens in vials of water to wash off the molasses residues, and either pin immediately afterward or transfer to 70% ethanol for longer term storage.  Some of the more desireable species I’ve collected in this manner, besides L. elaphus, are Plinthocoelium suaveolens, Purpuricenus axillaris, P. humeralis, P. paraxillaris, Stenocorus cylindricollis, S. shaumii, Sarosesthes fulminans, Stenelytrana emarginata [= Leptura emarginata], and S. gigas [= Leptura gigas].


Congratulations to Ben Coulter and Janet Creamer, both of whom correctly identified the species and most of the mouthparts.  Each earned 14 pts and, thus, tied for the win, while JasonC. earned 5 pts. to take the final podium spot.  The pointed structure is the labrum (its shape distinguishing it from other North American species of the genus), and it is flanked on each side by the fuzzy yellow galeae (derived from the maxillae) and the labial palps.  Nobody correctly named the galeae, which seem to be greatly elongated and hairy in stag beetles as a function of their sap feeding behavior.  A portion of the left maxillary palpus can also be seen in the corner of the photograph, but nobody scored those points either.  Brady Richards just missed the podium, but his witty reference to Gene Shalit (if not immediately picked up on by me) earns him an honorable mention.

With points being formally awarded now beginning with the previous competition (ID Challenge #1), I’ll start keeping an overall leaders board, and with wins in both competitions Ben takes a commanding lead in the overalls with 23 pts, followed by Janet Creamer at 14 pts and TGIQ at 8 pts.  I guess I should start thinking of some sort of tangible prize for winners periodically – suggestions welcome.  Stay tuned for another issue of Super Crop Challenge or ID Challenge in the near future.

REFERENCES:

Champlain, A. B. and J. N. Knull.  1932. Fermenting bait traps for trapping Elateridae and Cerambycidae (Coleop.).  Entomological News 43(10):253–257.

MacRae, T. C. 1991. The Buprestidae (Coleoptera) of Missouri.  Insecta Mundi 5(2):101–126.

MacRae, T. C. 1994. Annotated checklist of the longhorned beetles (Coleoptera: Cerambycidae and Disteniidae) known to occur in Missouri. Insecta Mundi 7(4) (1993):223–252.

Copyright © Ted C. MacRae 2010

Super Crop Challenge #3

/ Ted C. MacRae / 12 Comments

There are lots of points up for grabs with this one, what with several body parts to name as well as the organism to which they belong needing to be identified.  Rules and points will be awarded roughly as outlined in the inaugural ID Challenge – i.e., points are not mutually exclusive, with comment moderation turned on while the challenge is open to allow all a chance to participate (no advantage to those with trigger fingers).  Points will be awarded for correct taxonomic identifications (order, family, genus, and species – 2 pts each) and for each body part correctly names (2 pts each).  Bonus points may be awarded at my discretion for .

We’ll give this a day or so, depending on how quickly the answers come in…

Copyright © Ted C. MacRae 2010

My MT-24EX flash diffuser

/ Ted C. MacRae / 20 Comments

When I purchased my insect macrophotography rig two summers ago, I already knew that one of the biggest challenges I would face (besides a steep learning curve) was lighting.  While it is possible to do insect macrophotography using only natural light, this generally requires the use of a tripod and reflector for all but the largest of insects.  Unfortunately, such devices aren’t very practical for field photographs of the tiger beetles that I have come to enjoy stalking (and I already have enough to carry as it is without adding such incumbrances).  Supplemental flash lighting is a more attractive alternative for me – not only does it minimize the amount of equipment I must carry, but the high shutter speeds and small apertures it allows are perfect for ‘freezing’ subjects prone to quick movements while maintaining good depth-of-field. There are many flash units to choose from, but I went with the Canon MT-24EX Macro Twin Lite Flash for its dual light sources (eliminating the “flatness” of a traditional ring flash) and lightweight, front-of-lens mounted bracket (no need for heavy bracket extenders).  Combined with Canon’s 100mm f/2.8 (up to 1X magnification) or MP-E 65mm (1-5X magnification) macro lens, this flash unit has become quite popular in recent years for insect macrophotography. 

The problem with flash, of course, is the harsh, unnatural light that it produces.  With natural lighting, illumination comes from all directions, while with flash it is essentially unidirectional.  This is especially problematic with beetles, many of which have a smooth, shiny integument that reflects the flash to produce strong specular highlights.  Diffusion and maximizing the apparent size of the light source are key to achieving good results with flash units, and a variety of diffusers are commonly used to achieve this. Unfortunately, the small size of the MT-24EX flash heads and their placement at the front of the lens creates some unique challenges for diffusing their light.  The only commercially available diffusers for the MT-24EX (that I’m aware of) are the Stofen OM-24XSET, which are translucent plastic caps that fit over the unit heads.  I used these during my first season of photography, and while better than nothing they still leave much to be desired.  The problem is that they do nothing to increase the apparent size of the light source, and it is an even worse problem with the 100mm lens than the 65mm because of its longer working distance.  Much better results have been achieved by Kurt (Up Close with Nature) with his concave foam diffuser and Alex (Myrmecos) with his tracing paper diffuser.  Unfortunately, these diffusers only work with short focal length lenses such as the 65mm, while it is the 100mm lens that I use most often for tiger beetles (1.0-1.5X range).  For most of this past season, I tried a Gary Fong Puffer + Sto-Fen combo diffuser based on an idea by Dalantech, but again that setup seemed only slightly better than Sto-Fens alone with the 100mm.  As the season progressed, I continued to mull over various contraptions and ideas to extend the flash heads out in front of the lens to increase apparent light size.  Most of those ideas were expensive and bulky, but at the end of the season I came up with an idea that seemed like it might work and went with it.  The following photographs are the first iteration of that idea.

Canon MT-24EX flash and 100mm macro lens with DIY oversized concave diffuser.

The diffuser is a larger version of Kurt’s do-it-yourself (DIY) concave diffuser.  It uses thick polypropylene foam (used as padding in cardboard shipping boxes) that is sturdy enough to hold its shape but flexible enough to curl back and over the top of the flash heads, essentially forming a large “soft box” in front of both flash heads.

Diffuser is ultralight and lays almost flat when not installed - easily carried in camera backpack.

I cut the bottom inch off of a a 1,000-mL polypropylene beaker (the prototype used a 500-mL beaker, but that was too small).  I then cut the center out of the beaker bottom so that the hole size matched the lens opening of the flash head bracket, and then cut the beaker bottom in half.  This forms a sturdy but translucent, semi-circular frame to hold the polypropylene foam against the flash head bracket on the front of the lens.  The piece of foam measures 21″ (front) x 7″ (back) x 9″ (front to back) and is attached to the polypropylene frame using hot glue.

Flash heads extended forward w/ Kaiser shoes. Thin polypropylene foam layer taped over flash head.

I also used Kaiser shoes to extend the flash heads a little further forward in front of the lens, and I taped a small piece of thin polypropylene foam over front of each flash head to provide some initial diffusion.  This helps to increase the apparent light size by reducing the distance between the flash heads and the subject.  I snugged the pivot screw on the Kaiser shoes just enough to hold the flash head in place but still allow me to adjust their aim.

Diffuser attaches to front of flash bracket using Velcro strips.

The diffuser frame is attached to the front of the flash head bracket using pieces of Velcro strips.  It’s not a tight, sturdy connection, but so far I have not had any problems with the diffuser falling off.  This system allows me to quickly and easily switch out similar diffusers of different sizes (I have a smaller one that I made for the 65mm lens).

Diffuser attached to flash bracket.

Diffuser is curled back and corners attached to back of flash heads using Velcro.

Pieces of Velcro strip are also attached the corners of the diffuser and the back of the flash heads to hold the diffuser foam in position after attaching the bracket to the flash head bracket.

Diffuser in position and ready for use.

Diffuser remains properly positioned regardless of flash head position or lens changes.

I have since added additional Velcro strips along the front edge of the foam to allow it to be pulled back closer to the flash heads, depending on the distance to subject. 

One nice thing about this diffuser is that it does also work with the 65mm lens as long as there is nothing to get in the way of the diffuser.  It is simply a matter of angling the flash heads back closer to the lens and adjusting their aim according to the subject distance, then pulling the foam layer back closer toward them.  Or, just swap out with a smaller version.  When detached, the diffuser can be folded to lay flat in the backpack.

Of course, the proof is in the pudding, and none of this means anything if it doesn’t actually do the job.  I’m now immersed in the depths of a Midwestern winter, so I haven’t yet had a chance to test the diffuser in the field.  I have, however, done a fair amount of testing here in the laboratory using both live and dead insects and have been quite pleased with the results so far.  Those photographs can be seen in the following posts.  This coming season I’ll put it to the test in the field to see if it actually has the usability and durability that I have hoping for.

Copyright © Ted C. MacRae 2010