science

Use of extension tubes for better lighting

/ Ted C. MacRae / 17 Comments

The photos in this post of Tetracha floridana (Florida Metallic Tiger Beetle) illustrate a technique that I have begun using recently to improve the lighting in my full-flash insect macrophotographs—use of extension tubes!  I know this sounds strange, and I actually just stumbled onto it myself when I started using extension tubes in combination with my Canon EF 100mm macro lens.  Okay, I can hear it now: “Why not use the Canon MP-E 65 mm macro lens?”  It’s a good question, as at magnifications above 1X there is no finer lens than the 65mm.  However, the tiger beetles that I spend a lot of time photographing are right in that size range where sometimes I need magnifications below 1x (whole body shots of medium to large species), while other times I need magnifications above 1X (small species and closeups—particularly face shots).  Fortunately, the entire spectrum of magnifications (up to 5X) is covered by these two lenses, but there is, unfortunately, no overlap.  This is where the extension tubes come in—when all 68mm are added the 100mm lens effectively changes from a 1.0X–∞ lens to a 0.7–2.0X lens.  This gives a frame width of 11–33 mm, perfect for nearly all North American tiger beetles (most species range from 6-20 mm, excluding legs and antennae). 

In addition to allowing a more appropriate range of magnifications without the need to switch out lenses, this has one other effect—it moves the lens a little closer to the subject.  That in itself is of no particular benefit, but since I use the front-of-the-lens-mounted Canon MT-24EX dual flash, it also moves the flash a little closer to the subject.  It’s not a huge distance, only about 20 mm, but keep in mind that the flash heads extend forward from the front of the lens (especially with the Kaiser shoes that I use with my diffuser), and the front of the diffuser itself lies at about 60 mm in front of the lens face.  Thus, at 1X the the front of the diffuser sits ~80 mm from the subject with the 100mm lens only, but with 68 mm of extension tubes added it sits only 60 mm from the subject.  The closer the light source is to the subject, the greater the apparent light size, and larger apparent light size results in more even lighting with reduced specular effects.

Tetracha floridana | Pinellas Co., Florida (100mm lens only)

100mm lens + 68mm extension tubes

100mm lens only (slightly cropped)

100mm lens + 68mm extension tubes

The primary disadvantage to doing this is loss of ability to focus to infinity.  Frankly, this is functionality I never used with the 100mm lens, preferring instead the 17-85mm wide-angle lens for more general landscape and habitat photos.  The other downside is that placing the lens closer to the subject can result in greater chance of “spooking” the subject and causing it to flee or behave evasively.  Again, however, my experience is that if a subject can be photographed at 1X with the 100mm lens, it can be photographed at 2X with the 100mm lens + extension tubes.

Has anybody else ever tried this, and if so what was your experience?

Copyright © Ted C. MacRae 2011

Charming Couple revisited

/ Ted C. MacRae / 4 Comments

Another view of the of Ellipsoptera hamata lacerata (Gulf Coast Tiger Beetle) that I photographed in a small mangrove marsh in Seminole, Florida. These are actually among the first tiger beetles that I ever tried to photograph at night, and the major learnings involved: 1) figuring out how to turn on the flash lamp and then compose the shot quickly enough before the lamp shut off, and 2) making sure to use the histogram in the field to ensure I’d gotten the proper flash level. My first few attempts all tended to be underexposed because the brightness of the image on the playback screen in the darkness caused me to keep undersetting the flash exposure compensation. I’d not previously gotten in the habit of using the histogram in the field since I do a lot of flash level bracketing, but perhaps this is a tool that will allow me to cut down on that to some degree. Anyway, these are two additional photos that worked out pretty well—I like the first because of the contrast between the bright white mandibles of the male versus the off-white mandibles of the female, and the second (female only after the male bolted) for its nice view of the curiously bent elytral apices that distinguish it from the female of the very similar and (in this area) sympatric E. marginata (Margined Tiger Beetle). Also clearly seen in the second is one of the distinct basolateral grooves on the pronotum that serve to receive the male mandibles during mating (compare to same area on pronotum of male). I was amazed at how easy this mating pair and other individuals of this species were to photograph at night in view of their extreme wariness during the day.

Ellipsoptera hamata lacerata | Seminole, Pinellas Co., Florida

Note curiously bent elytral apices and basolateral pronotal groove for reception of male mandibles.

Copyright © Ted C. MacRae 2011

Gnom, Gnom, Gnom…

/ Ted C. MacRae / 9 Comments

I’ve become a big fan of night-time tiger beetle photography since my early August trip to Florida.  Not only does it open up the world of nocturnal species that might go undetected during the day, it also affords the opportunity to see diurnal species engaged in behaviors that are more difficult to photograph during the day.  This female Gulf Beach Tiger Beetle (Ellipsoptera hamata lacerata) came to my blacklight at a coastal salt marsh near Steinhatchee and promptly began munching on a smaller beetle that had also come to the light.  I didn’t get a good enough look at the prey early on to identify it, and by the time I was able to zoom in big with the camera lens the prey had already been macerated to a crunchy pulp.  It was interesting to watch the tiger beetle grasp and chew the prey with its mandibles while manipulating its position with its maxillary parts.




Copyright © Ted C. MacRae 2011

Why I Roamed the Marsh at Night

/ Ted C. MacRae / 22 Comments

Tetracha floridana (Florida Metallic Tiger Beetle) | Pinellas Co., Florida

For two years I waited.  The narrow strip of coastal scrub and mangrove marsh along the intracoastal waterway behind my sister-in-law’s condominium in Seminole, Florida had been an unexpected surprise during my first visit in August 2009.  Despite its small size and urban surroundings, it proved to be a good spot for tiger beetles, including Ellipsoptera marginata (Margined Tiger Beetle) and the closely related E. hamata lacerata (Gulf Coast Tiger Beetle).  Also living there was a much rarer tiger beetle—the Florida-endemic species Tetracha floridana (Florida Metallic Tiger Beetle), but I did not know this at the time.  In fact, had I not happened upon some larval burrows as I was leaving the preserve and decided to collect a few and rear them to adults, I would still not know they were there.  Only after the two larvae that made it back to St. Louis alive emerged as adults in their rearing container did I realize what I had found.  The reason I had not seen any adults during my visit was simple—they, like all members of the genus to which they belong, are strictly nocturnal!  Nevertheless, I knew I would return sooner or later and have another shot at seeing adults of this species in the wild.

A male, distinguishable by the thick brushy pads on the front tarsi.

And return I did.  My wife and I decided fairly early this year that we wanted to return to Florida for our summer vacation.  She likes the beach and her sister, and the kids like the beach and their aunt.  I don’t like the beach so much (though my sister-in-law is pretty cool), but I love Florida for its diversity of tiger beetle species and their high level of endemism.  During my 2009 trip I managed to find nine species, which, in addition to T. floridana, included also the very rare and potentially threatened Cicindelidia highlandensis (Highlands Tiger Beetle), known only from the Lake Wales Ridge in central Florida, and the (near) endemic Ellipsoptera hirtilabris (Moustached Tiger Beetle).  This year I set my sight on several other endemics—e.g. Cicindelidia floridana (Miami Tiger Beetle)—and near-endemics—e.g. Cicindelidia scabrosa (Scabrous Tiger Beetle).  My searches for these targets would have to wait for a few days, but for T. floridana I had only to wait until nightfall on the day we arrived.  The bleating chorus of tree frogs was my signal, and as the rest of the family retired to their bedrooms I geared up with my collecting fanny pack, camera bag and headlamp and headed out to the marsh.

The species lacks the violaceous reflections found on the elytra of T. carolina.

As I mentioned in my previous post, it was a little unnerving to walk into the marsh surrounded by darkness and greeted by scuttling hordes of sea slaters.  The anticipation of finally seeing T. floridana, however, was more than enough motivation to forge onward while deliberately scanning the ground with my headlamp.  For some amount of time I focused on the more barren areas, which is where I would have expected the adults to occur, but only after I also began scanning some of the sparsely vegetated ground—typically slightly elevated above the moister and more barren areas—did I see the first adult.  Its agile dash into and through the vegetation upon my approach was a little surprising and required more effort than I expected to finally capture it.  Elation!  Finding rare species is always a treat, but it is extra special when you find one where nobody previously knew it existed.  Over the course of the next 1½ hours (as well as the following night and two nights after that) I would see countless adults, giving me comfort that I could collect a reasonable voucher series without causing negative impacts on the population.

A female oviposits in the soil amongst the sparse, salt-tolerant vegetation.

I had hoped to see mating pairs but never did; however, I did find a female in the act of oviposition.  Consistent with the apparent adult preference for sparsely vegetated areas rather than barren ground, the female was nestled amongst the vegetation while she excavated a hole for the egg she would lay.  On the last night that I visited the marsh, I focused my efforts on finding larval burrows, starting in the area where I had seen them two years ago.  I only found a few but succeeded in fishing one 3rd-instar larva out of its burrow.  You see, even though I photographed one two years ago, the larva of this species remains undescribed in the literature.  Since I allowed the two larvae I had collected to complete their development to adulthood, I still lacked preserved specimens that could be used for the basis of a description.  I now had one, but for a formal description it would be better to have at least a few examples.  Remembering that I had seen the female ovipositing amongst vegetation rather than out in the open, I began searching the nearby vegetated areas for burrows.  This approach was met with better success, and from the dozen or so burrows that I was able to find, I succeeded in fishing out two more 3rd-instars.  I already have several preserved larvae of Tetracha virginica (Virginia Metallic Tiger Beetle) and a single T. carolina (Carolina Metallic Tiger Beetle) collected in southeastern Missouri by my good friend Kent Fothergill—this small series of T. floridana now leaves me lacking only the also-undescribed T. impressa (Upland Metallic Tiger Beetle) among the four North American (sensu stricto) species of Tetracha.  I will be anxious to compare the larvae of T. floridana I now have with those of T. carolina and T. virginica in an effort to find species-specific characters.

This male is sporting some very impressive teeth on his mandibles.

Copyright © Ted C. MacRae 2011

Creepy Crawly Crustaceans

/ Ted C. MacRae / 11 Comments

During my early August trip to the Gulf Coast of Florida, I spent several nights exploring the small mangrove marsh behind my sister-in-law’s condominium in Seminole. There were other reasons for me wanting to do this that will be revealed in a future post, but suffice it to say that, to this land-locked Midwesterner, the intertidal zone between land and sea is a strange and weird place. The plants are strange—long aerial roots, salt exudate-covered leaves, succulent jointed stems; and the animals are strange—molluscs and crustaceans featuring just as prominently as the insects with which I am more familiar. Even the smells are strange. Add to that the cover of darkness and it seems downright alien. For me, stumbling through the marsh with only the bright tunnel of light from my headlamp to reveal whatever lurks in the surrounding blackness seemed like a walk on another planet—new, exciting, and a tad unnerving!


As I took those first tentative steps through the marsh, one of the first things I noticed scuttling across the moist ground were what looked to me like giant wood lice.  Terrestrial isopods (class Malacostraca, order Isopoda) are nothing new to me—”roly-polys” and wood lice are common where I live, but I have never seen any as large as these, measuring as much as 25-30 mm in length (that’s an inch or more, folks!), not even counting their quite long antennae and uropoda.  They were also quite numerous, abundant actually.  I must confess to feeling a little creeped out at first upon seeing them—I could just imagine these strange, alien creatures suddenly swarming all over me and devouring the flesh from my body under the cover of darkness.  Okay, it was more of a fleeting thought than a palpable fear, but it has been awhile since I’ve encountered an arthropod with which I am so completely unfamiliar.  During the course of the night I photographed a number of individuals, not knowing what characters might be most important for identification and hoping that maximizing the number of photographs would increase my odds of getting the right shot.  Once I sat down to figure out what they were, the answer came quickly, as there is really nothing quite like sea slaters (genus Ligia).  Several species of these apparently common residents of intertidal zones are found on both the Atlantic and Pacific Coasts (Schmalfuss 2003), where they hide during the day and come out at night to scavenge on algae and whatever other organic matter they can find.




Despite my initial thought that a species ID might not be possible, I was eventually able to determine with a fair degree of confidence that the individuals in these photos represent L. baudiniana.  This species is distinguished from two other species in the genus in Florida (Schultz and Johnson 1984) by the combination of its long uropoda (L. oceanica—introduced from Europe—has the uropoda much less than 2/3 the length of the body) and brush-like structures on the first pair of legs of the male, visible in the middle photograph above (L. exotica males lack these structures and possess instead a process at the distal end of the leg). These characters are illustrated nicely in Richardson (1905), which despite its great age seems to still to be a relevant resource for the family in North America.


Congratulations to Morgan Jackson, who wins Super Crop Challenge #8 with 11 points and distinguishes himself as the only participant to correctly identify the species.  Dave and Roy complete the podium with 9 points each.  In the overalls, two-time Session Champ Ben Coulter earned 8 pts to retain his lead with 22 pts, while Mr. Phiddipus and Roy move into a tie for 2nd place just 4 pts off the lead.  It’s still early, but this is shaping up to be a competitive session!

In the next post, I’ll reveal the real reason I was so interested in searching this marsh at night…

REFERENCES:

Richardson, H.  1905.  A monograph on the isopods of North America.  Bulletin of the United States National Museum 54:i–liii, 1–727.

Schmalfuss, H. 2003. World catalog of terrestrial isopods (Isopoda: Oniscidea). Stuttgarter Beiträge zur Naturkunde (Serie A) 654:1–341 [revised and updated online version].

Schultz, G. A. and C. Johnson. 1984. Terrestrial isopod crustaceans from Florida (Oniscoidea). Tylidae, Ligiidae, Halophilosciidae, Philosciidae, and Rhyscotidae. Journal of Crustacean Biology 4(1):154-171. 

Copyright © Ted C. MacRae 2011

Super Crop Challenge #8

/ Ted C. MacRae / 23 Comments

Here’s a face you don’t see that often (or at least I don’t).  There’s little doubt about what body parts are shown here, so rather than awarding points for naming structures we’ll treat this as a standard ID Challenge.  However, the categories are a little different from the usual—2 pts each for class, order, family, and genus (I suspect a species ID may not be possible, at least from this photo).  Standard challenge rules apply, including moderated comments (to give everyone a chance to take part) and bonus points awarded on a discretionary basis for a variety of reasons, e.g. as tie-breakers if multiple participants arrive at the same correct answer, providing additional relevant information, humor, etc.  

Reminder: I am quite the pedant—points can be awarded or taken away depending on one’s attention to detail.  Also, when all else fails pity points will be awarded.


Good luck!

Copyright © Ted C. MacRae 2011

The (almost) Florida-endemic Cicindelidia scabrosa

/ Ted C. MacRae / 9 Comments

The recently rediscovered Cicindelidia floridana (Miami Tiger Beetle) may have been the highlight of my 48-hour early August blitz through Florida, but it was by no means the only Florida-endemic that I hoped to find during the trip.  In fact, the day before I saw C. floridana I found the species it was formerly considered a subspecies of, C. scabrosa (Scabrous Tiger Beetle), itself an almost Florida-endemic (its distribution extends just north of the border into extreme southeastern Georgia).  I had word that I might find the species in sand pine scrub habitat along the Gulf Coast around Lower Suwanee National Wildlife Refuge and Cedar Key Scrub State Preserve (Levy Co.).  This area lies very near yet another locality (where I was hoping to find yet another Florida-endemic), further justifying my decision to travel several hours north the day before I was to retrace my route back to the south and then continue on down to Naples to meet up with Dave Brzoska and Chris Wirth for the trip to Miami to see C. floridana.

Cicindelidia scabrosa (Scabrous Tiger Beetle) | Levy Co., Florida

Cicindelidia scabrosa is one of four small, sand-dwelling species with red venters collectively referred to as the abdominalis-species group (Brzoska et al. 2011).  The nominate species, C. abdominalis (Eastern Pinebarrens Tiger Beetle), is the most widespread member of the group, occurring across the Southeastern U.S. Coastal Plain from Maryland and New Jersey to Louisiana (Pearson et al. 2006).  The three remaining species are Florida-endemics (C. floridana and C. highlandensis—Highlands Tiger Beetle) or near endemic (C. scabrosa), presumably evolving during the Pleistocene Epoch (1.8 million to 10,000 years ago) at a time when fluctuating sea levels repeatedly isolated peninsular Florida from the mainland.  I found both C. abdominalis and C. highlandensis during my 2009 trip, so finding C. floridana and C. scabrosa on this trip means that I have now seen all four members of the abdominalis-species group.

Black, sculptured elytra and dense lateral bands of pronotal setae distinguish this species.

There is little doubt about the distinctiveness of C. scabrosa compared to C. abdominalis and C. highlandensis, as neither of the latter two species exhibit the distinctly scabrous elytra or rows of flattened setae on the sides of the pronotum exhibited by C. scabrosa.  The distinction of C. scabrosa from C. floridana, however, is more subtle—C. scabrosa is shiny black and always exhibits a post median marginal spot anterior to the apical lunule, while C. floridana is shiny green and usually lacks the post median marginal spot.  In addition, the legs of C. floridana are somewhat lighter in coloration than those of C. scabrosa.  The difference in coloration is subtle in preserved specimens but obvious in living individuals.  After seeing the C. scabrosa in the field one day and C. floridana the next, my first thought regarding the latter was, “Wow, that’s different!”—a result of the brilliant coppery highlights that are quite evident in living individuals but apparently fade in preserved specimens.

Sand pine scrub, habitat for Cicindelidia scabrosa and Ellipsoptera hirtilabris

The distinction between C. scabrosa and C. floridana is not limited to subtle morphological characters—included also are differences in habitat, distribution, and seasonal occurrence.  Cicindelidia scabrosa occurs broadly across the Florida peninsula in sand pine scrub, a xeromorphic plant community featuring an open canopy of sand pine (Pinus clausa) growing on well-drained, infertile, sandy soils (Brzoska et al. 2011).  The species is absent, however, from much of south Florida where the wet areas of the Everglades limit availability of suitable habitat.  Cicindelidia floridana, on the other hand, is restricted to a small area of Miami-Dade County and parts of the Keys where pine rockland habitat, a savanna-like forest of Florida slash pine (Pinus elliotti var. densa) and scrub understory, can be found growing on limestone outcrops.  The photos in this post were taken on an open 2-track through sand pine scrub near Cedar Key Scrub State Preserve.  Occurring here in asscociation with C. scabrosa was another (almost) Florida-endemic tiger beetle, Ellipsoptera hirtilabris (Moustached Tiger Beetle), which I have also seen in association with C. abdominalis and C. highlandensis (but not C. floridana).

The obligatory face shot!

It is perhaps redundant for me to state that it was extraordinarily hot while I photographed these beetles.  Temperatures were already approaching 90°F when I found the first individuals, and by mid-day when they finally disappeared it was nearly 100°F.  Add to that the mid-summer Florida humidity, and I was about as soaked as I ever get. It’s a photographer’s nightmare—trying to protect expensive gear while scrumming through the sand and sweating profusely, all the while still trying to get the perfect shot!  The beetles were smart enough to call it a day at 12:30 p.m., and I must say I didn’t mind having to get into an air-conditioned car, chug a quart of ice-cold Gatorade, and spend the next several hours not broiling under the hot Florida sun while making the long drive south.

REFERENCES:

Brzoska, D., C. B. Knisley, and J. Slotten.  2011.  Rediscovery of Cicindela scabrosa floridana Cartwright (Coleoptera: Cicindelidae) and its elevation to species level. Insecta Mundi0162:1–7.

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

Predator or Prey?

/ Ted C. MacRae / 25 Comments

Ellipsoptera hamata lacerata | Dixie Co., Florida

Everyone knows that tiger beetles are predators, but look closely at the underside of the head of this female Ellipsoptera hamata lacerata (Gulf Beach Tiger Beetle), photographed in a coastal marsh in Dixie Co., Florida earlier this month.  See the ant head attached by its mandibles to the base of the tiger beetle’s left maxillary palpus?  Detached ant heads latched onto the palp or antenna of a tiger beetle are a fairly common sight—Pearson and Vogler (2001) show the head of an ant attached to the antenna of Eunota togata (Cloaked Tiger Beetle), and Pearson et al. (2006) show one attached to the antennae of Cicindela formosa (Big Sand Tiger Beetle).  I’ve also photographed Cylindera celeripes (Swift Tiger Beetle) with an ant head attached to its antenna.  Pearson and Vogler (2001) and Pearson et al. (2006) both suggest that the ant heads are the result of predation attempts by groups of ants attempting to overpower and kill the tiger beetle, making the ants the predators and the tiger beetles the prey.

Note ant head attached by its mandibles to the base of the tiger beetle's left maxillary palpus.

Although some ants are well known for their predatory horde behavior, I’m not sure I buy this as an explanation for the common occurrence of ant heads attached to tiger beetles.  Tiger beetles themselves often prey on ants, and while I have seen numerous tiger beetles with ant heads attached to them, I have never seen one actually being overpowered by ants (scavenging an already dead tiger beetle, yes—but not overpowering and killing one).  Moreover, the ant heads are nearly always attached to the base of an antenna or palpus—right next to the tiger beetle’s mouth, and almost never on more distal parts of the antennae or other parts of the body.  If the ants were attempting to prey on the tiger beetle, wouldn’t they also (if not even more commonly) be found attached to the tiger beetle’s legs or soft intersegmental membranes?  And how would the ants have come to be decapitated while in the act of attempting to overpower the beetle?  I suggest it is more likely that the ants were prey, latching onto the nearest part of their killer’s body in a last ditch attempt to avoid their inevitable fate.  The antennal and palpal base are about the only tiger beetle body parts that would be within reach of an ant in a tiger beetle’s toothy grasp.  While the rest of the ant was consumed, the head remained because it was firmly attached to the beetle.

I realize that an identification based only on the detached head of an ant may be difficult, but if one is possible it would be appreciated.  The ant head shown in Pearson and Vogler (2001) was identified as Polyergus sp.

REFERENCES:

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.

Pearson, D. L. and A. P. Vogler.  2001. Tiger Beetles: The Evolution, Ecology, and Diversity of the Cicindelids.  Cornell University Press, Ithaca, New York, 333 pp.

Copyright © Ted C. MacRae 2011