A “Really” Big-headed Tiger Beetle

November 24, 2009October 10, 2011 / Ted C. MacRae / 4 Comments

Megacephala megacephala 3rd-instar larva. Photo © Artur M. Serrano.

In my recent summary of the latest issue of the journal Cicindela, I included a scan of the cover of that issue and its stunning image of the 3rd-instar larva of Megacephala megacephala¹ from Africa. This otherwordly-looking, four-eyed beast was photographed with jaws agape at the entrance to its burrow in Guinea Bissau by Dr. Artur M. Serrano (University of Lisbon, Portugal). I was grateful for his permission to post a scan of this spectacular image; however, he did even better and sent me high-resolution images of not only the larva (above) but the adult (below) as well. This species is one of 13 assigned to the genus—presently restricted to Africa (though not always, see discussion below), where they are usually found in savanna-type habitats and are active during the crepuscular and nocturnal periods (Werner 2000).

¹ An example of a tautonym, i.e. a scientific binomen in which the genus and species names are identical. Familiar tautonymic binomina include the gorilla (Gorilla gorilla), green iguana (Iguana iguana), and European toad (Bufo bufo). Tautonyms are expressly prohibited in plant nomenclature (see Article 23.4 of the International Code of Botanical Nomenclature) but are permitted and, in fact, quite common in zoological nomenclature; Wikipedia lists 51 mammals, 82 birds, 15 reptiles & amphibians, 54 fish, and 33 invertebrates (though not Megacephala megacephla!).

Megacephala megacephala adult. Photo © Artur M. Serrano.

For those of you who see a strong resemblance by this species to another tiger beetle I featured recently, Tetracha floridana (Florida Metallic Tiger Beetle), this is not merely a coincidence. Megacephala and Tetracha are quite closely related, and in fact the two genera, along with a handful of other closely related genera, are at the center of one of the longest-standing disputes in tiger beetle taxonomy (Huber 1994). The genus Megacephala was established by Latreille (1802) for the species pictured here (originally described as Cicindela megacephala Olivier). As additional taxa were found in Africa, Australia and the Western Hemisphere and assigned to Megacephala, several workers attempted to divide the genus into multiple genera (with New World taxa being assigned to Tetracha and a few other mostly South American genera); however, there was little agreement on how these genera should be defined and on what characters they should be based. The debate was effectively swept under the rug in the early 20th Century when Walter Horn, one of the most influential cicindelophiles of all time, accepted a monotypic Aniara based on the strange South American species A. sepulcralis but reunited the world’s remaining taxa within the single genus Megacephala in his world catalogue (Horn 1910). Horn’s use of Megacephala as a catch-all genus was followed by subsequent workers for almost a full century until Huber (1994) once again proposed restricting Megacephala to certain of the African species and resurrecting the genus Tetracha for the bulk of the New World fauna. He also urged additional analyses to resolve the status of the remaining generic names and their composition, which subsequently saw increasing use as subgenera of Megacephala² and later as genera.

² Thus, as type-species for the genus, the species featured here became known as Megacephala (Megacephala) megacephala (Werner 2000)—a triple tautonym that translates to the “Big-headed, Big-Headed, Big-Headed” tiger beetle! Perhaps it’s best that I’m not an African tiger beetle specialist; I probably would have been unable to resist the temptation to resurrect M. senegalensis and assign it as a subspecies of M. megacephala, just so I could refer to the nominate form as Megacephala (Megacephala) megacephala megacephala!

The reversal of Horn’s concepts now appears to be complete, with all seven former subgenera of Megacephala formally being accorded full generic status (Naviaux 2007). This classification is strongly supported by molecular analysis of nuclear 18S and mitochondrial 16S and cytochrome oxidase gene sequences (Zerm et al. 2007), with the resulting dendrogram indicating three monophyletic clades corresponding to the African/Palearctic (Megacephala and Grammognatha, respectively), Western Hemisphere (Aniara, Metriocheila, Phaeoxantha and Tetracha) and Australian (Australicapitona and Pseudotetracha) genera³. The African/Palearctic clade was found to occupy a basal position in the tree, while the Western Hemisphere and Australian clades were more derived. These data support the hypothesis that the early evolution of the megacephalines took place during the break-up of the ancient Gondwana megacontinent, which began about 167 million years ago (middle Jurassic period) and sequentially disconnected Africa from South America and Australia.

³ One striking deviation from the current classification, however, was the support for nesting the single Aniara species within Tetracha, a placement that renders Tetracha paraphyletic and, thus, requires either its division into multiple genera or the sinking of Aniara as a distinct genus. The support for this placement was quite strong and mirrored the results of a broader molecular phylogenetic study of tiger beetles based on full-length 18s RNA data (Galian et al. 2002). The authors concede that this puzzling placement is not corroborated by numerous morphological, ecological and ethological characters that distinguish Aniara from all known Tetracha species.

REFERENCES

Galián J., J. E. Hogan and A. P. Vogler. 2002. The origin of multiple sex chromosomes in tiger beetles. Molecular Biology and Evolution 19:1792–1796.

Horn, W. 1910. Coleoptera Adephaga, Fam. Carabidae, Subfam. Cicindelinae. In P. Wytsman (editor). Genera Insectorum. Fascicle 82a. Desmet-Vereneuil, Brussels, Belgium, pp. 105–208.

Huber, R. L. 1994. A new species of Tetracha from the west coast of Venezuela, with comments on genus-level nomenclature (Coleoptera: Cicindelidae). Cicindela 26(3/4):49–75.

Latreille, P. A. 1802. Histoire Naturelle, Générale et Particulière des Crustacés et des Insectes. Paris: F. Dufart 3 xii 13 + 467 pp.

Naviaux R. 2007. Tetracha (Coleoptera, Cicindelidae, Megacephalina): Revision du genre et descriptions de nouveaus taxons. Mémoires de la Société entomologique de France 7:1–197.

Werner, K. 2000. The Tiger Beetles of Africa (Coleoptera: Cicindelidae). Volume 1. Taita Publishers, Hradec Kralove, Czech Republic, 191 pp., 745 figures.

Zerm, M., J. Wiesner, J. Ledezma, D. Brzoska, U. Drechsel, A. C. Cicchino, J. P. Rodríguez, L. Martinsen, J. Adis and L. Bachmann. 2007. Molecular phylogeny of Megacephalina Horn 1910 tiger beetles (Coleoptera: Cicindelidae). Studies on Neotropical Fauna and Environment 42(3):211–219.

Moustached Tiger Beetle

November 16, 2009October 10, 2011 / Ted C. MacRae / 14 Comments

Dry sand scrubland on Lakes Wales Ridge in central Florida—home to Cicindela highlandensis and Ellipsoptera hirtilabris

In my previous post, I featured the rare Cicindela highlandensis (Highlands Tiger Beetle), restricted entirely to sand scrubland and pine woodland habitats along the Lake Wales Ridge in central Florida (Choate 2003). However, that would not be the only Florida endemic tiger beetle that I would encounter during my early August visit. Another of the several tiger beetle species that I’d hoped to see would also be found that day, although in much lower numbers. Ellipsoptera hirtilabris (Moustached Tiger Beetle) is so named¹ because of the dense covering of prostrate hairs on its labrum that distinguish it from the closely related E. gratiosa (Whitish Tiger Beetle). Both of these species exhibit striking white maculations that cover almost the entire elytral surface and dense white pubescence covering the head, thorax, underside and legs. They are the only species of the genus occurring in Florida, but their ranges do not overlap (Pearson et al. 2006)—E. gratiosa occurs in the coastal pine barrens of Virginia, the Carolinas, southern Georgia and the Florida panhandle, while E. hirtilabris is restricted to peninsular Florida in pine woodlands, sand hills and other habitats with open white sand. Although the latter is considered a Florida endemic, it has been found just outside of Florida in extreme southeastern Georgia on St. Simon’s Island (Choate 2003). In addition to the pubescence of the labrum and their allopatric distributions, the two species may further be distinguished by the slightly less expanded markings and more diffuse edges where they contact the central bronze area in E. hirtilabris and the slightly larger size of E. gratiosa. Like C. highlandensis and C. abdominalis, it seems likely that E. hirtilabris and E. gratiosa evolved from a common ancestor, diverging in isolation from each other during the pre-Pleistocene separation of peninsular Florida from the North American mainland.

¹ The species epithet is derived from the Latin words hirtum meaning “hairy” and labrum meaning “lip”.

Ellipsoptera_hirtilabris_IMG_1091_1200x800_enh

Ellipsoptera hirtilabris in the alert position

I found E. hirtilabris to be exceedingly difficult to see and photograph. Unlike C. highlandensis, which resemble bits of debris laying on the surface of the white sands where it lives, the largely white E. hirtilabris blend into the white sand itself and are almost impossible to see until they move. The small bronze-colored patches along the elytral suture augment their cryptic capabilities by resembling small bits of debris, which is especially evident in the photo below. Both Pearson et al. (2006) and Erwin and Pearson (2008) state that adults of this species freeze in position when approached, which may be the reason why I saw so few individuals. Once I did see them, they were extremely wary and difficult to photograph no matter how cautiously I approached. The photos shown here represent the only two individuals that I succeeded in photographing, and in neither case did I succeed in getting a frontal perspective to show the pubescent labrum (stifling heat and oppressive humidity during the photo session did not help matters, either).

Ellipsoptera_hirtilabris_IMG_1131_1200x800_enh

The white coloration with small brown markings helps adults blend in perfectly in their white sand habitats

Photo details:
Photo 1: Canon 100mm macro lens on Canon 50D (landscape mode) ISO-100, 1/250 sec, f/16, natural light.
Photos 2 & 3: Manual mode, f/25, MT-24EX flash w/ Sto-Fen diffusers @ 1/8 ratio.

REFERENCES:

Choate, P. M., Jr. 2003. A Field Guide and Identification Manual for Florida and Eastern U.S. Tiger Beetles. University Press of Florida, Gainesville, 224 pp.

Erwin, T. L. and D. L. Pearson. 2008. A Treatise on the Western Hemisphere Caraboidea (Coleoptera). Their classification, distributions, and ways of life. Volume II (Carabidae-Nebriiformes 2-Cicindelitae). Pensoft Series Faunistica 84. Pensoft Publishers, Sofia, 400 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.

Highlands Tiger Beetle

November 12, 2009October 10, 2011 / Ted C. MacRae / 11 Comments

When my wife and I made plans to spend a week at her sister’s condominium in Florida this past summer, I began making a list of the tiger beetle species that I wanted to see. I would be happy to see anything, since I had never before tiger beetled in Florida, but early August was looking to be on the late side for many things. In addition, since this was a family vacation, I would only have a couple days at most to sneak off on my own and immerse myself in bug hunting. All this meant that I would have to be very judicious about where I went and what I looked for. I sought advice from a few other cicindelophiles on species and localities, and by the time we made the 16-hour drive from St. Louis to Seminole (near St. Petersburg) I had settled on two destinations—the Lake Wales Ridge of central Florida to look for Cicindela highlandensis (Highlands Tiger Beetle), and the so-called “Road to Nowhere” near Steinhatchee where as many as 10 species of tiger beetles can be seen when the season is right. Things started out well when, before even looking for any of these species, I stumbled upon Ellipsoptera marginata (Margined Tiger Beetle), its sibling species E. hamata lacerata (Gulf Beach Tiger Beetle), and some 3rd-instar larvae in their burrows that proved to be the Florida endemic Tetracha floridana (Florida Metallic Tiger Beetle) in the small coastal preserve just outside the back door of my sister-in-law’s condo.

Dry sand scrubland on Lakes Wales Ridge in central Florida

The big target of the trip, however, was not so straightforward. Cicindela highlandensis is one of Florida’s rarest endemic tiger beetles, being restricted entirely to remnant sand scrubland and pine woodland habitats along the Lake Wales Ridge of Polk and Highlands Counties in central Florida (Choate 2003). The Lake Wales Ridge represents former shorelines deposited when the rest of peninsular Florida was covered by seas. The quick draining sands have created desert-like open habitats dominated by oaks, pines, and other drought-tolerant species. Cicindela highlandensis is one of many plants and animals endemic to the Lake Wales Ridge, which has the highest concentration of endangered plants in the continental U.S. Unfortunately, the natural communities found on the Lake Wales Ridge have suffered severe reductions from their historical occurrence. An estimated 85% of the scrub and sandhills has been converted to citrus groves and urban developments, and the few remaining tracts face not only continued development pressure, but also the threat of degradation from reductions in the frequency and extent of the wildfires that are essential for their maintenance (Turner et al. 2006). NatureServe (2009) estimates that C. highlandensis populations have declined by as much as 90%, and only a few of the sites where it is known to occur are large enough to sustain viable populations. While the species has a global status of G1 (critically imperiled) due to its limited range, restricted habitat, and very small population size, and is a candidate for listing as an endangered species by the U.S. Fish & Wildlife Service (Pearson et al. 2006), it remains—bafflingly—unlisted even as threatened by the State of Florida. As a result, there is no formal conservation management plan for this species to ensure its survival. Fortunately, the largest populations of C. highlandensis occur on an assemblage of public and private lands that are under partial to full conservation ownership, and preservation/management activities are taking place at most of these.

Cicindela_highlandensis_IMG_1126_1200x800_enh

Cicindela highlandensis, Highlands Tiger Beetle, in alert position

I had debated whether to look for Cicindela highlandensis at all—not because I wasn’t anxious to see it, but because I lacked confidence that I would be able find it. A late season search for a rare species had all the hallmarks of a potential wild goose chase. Nevertheless, I like a good challenge, and I had succeeded in obtaining information about specific locations for the species (a matter of public record; however, I prefer to maintain some discretion in this venue). Although I began my search with tempered optimism, it didn’t take long for me to acheive my goal. Similar to my experience with Cylindera celeripes in Oklahoma, I had barely walked ten yards into a gorgeous sand scrub habitat at the first site I had planned to search before I saw an individual. The dark metallic blue coloration of the species would seem to make it easily seen in its white sand environs; however, in reality it is almost impossible to see until it moves. Some have suggested that its coloration functions to make the beetle resemble the many small pieces of debris that litter the sand surface—perhaps the bits of charred wood that are common in open, fire-mediated environments. Its dependence upon natural disturbance factors such as fire was made apparent to me by the distinct preference I noted for adults to congregate along trails kept open by human disturbance, and to a lesser degree in the larger, naturally open scrub areas. The adults made very short escape flights and were easy to follow but difficult to approach closely enough for photographs due to extreme wariness—their long legs giving some indication of their highly cursorial capabilities.

Cicindela highlandensis - note absence of setae on thorax and abdomen

Cicindela highlandensis is closely related to two other species of tiger beetles in Florida—C. abdominalis (Eastern Pinebarrens Tiger Beetle), widely distributed throughout the Atlantic and Gulf Coastal Plain, and C. scabrosa (Scabrous Tiger Beetle), confined to the Florida Peninsula and adjacent southeastern Georgia. Both of these species are absent from the Lake Wales Ridge and, thus, do not co-occur with C. highlandensis. It is likely that C. highlandensis evolved from isolated populations of the widespread C. abdominalis that diverged during pre-Pleistocene separation of the Lake Wales Ridge from the mainland (Choate 1984). Despite its resemblance to both C. abdominalis and C. scabrosa, C. highlandensis can be distinguished from both of those species by the complete absence of flattened, white setae on the sides of the prothorax and the abdomen and by the highly reduced or absent elytral maculations (note the very small apical markings on the individuals in these photographs). All three of these species belong to the subgenus Cicindelidia (American Tiger Beetles) and possess red adominal coloration that is prominent during flight.

Photo details:
Photo 1: Canon 17-85mm zoom lens on Canon 50D (landscape mode), ISO-100, 1/160 sec, f/13, natural light.
Photos 2–3: Canon 100mm macro lens on Canon 50D (manual mode), ISO-100, 1/250 sec, f/14 (photo 2) or f/20 (photo 3), MT-24EX flash w/ Sto-Fen diffusers.

REFERENCES:

Choate, P. M., Jr. 1984. A new species of Cicindela Linnaeus (Coleoptera: Cicindelidae) from Florida, and elevation of C. abdominalis scabrosa Shaupp to species level. Entomological News 95:73–82.

Choate, P. M., Jr. 2003. A Field Guide and Identification Manual for Florida and Eastern U.S. Tiger Beetles. University Press of Florida, Gainesville, 224 pp.

NatureServe. 2009. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. Available at: http://www.natureserve.org/explorer (accessed: November 12, 2009).

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.

Turner, W. R., D. S. Wilcove and H. M. Swain. 2006. State of the scrub: conservation progress, management responsibilities, and land acquisition priorities for imperiled species of Florida’s Lake Wales Ridge. Archbold Biological Station, Lake Placid, Florida, iii + 44 pp.

Beetle Research Roundup

November 5, 2009October 10, 2011 / Ted C. MacRae / 14 Comments

The latest issue of the journal Cicindela arrived in my mailbox today, and as usual some interesting papers are included. For those of you unfamiliar with it, Cicindela is “a quarterly journal devoted to the Cicindelidae,” publishing papers dealing with any aspect of the study of tiger beetles. Founded in 1968 by North American tiger beetle experts Ronald L. Huber, Robert C. Graves, and Harold L. Willis, it was dubbed in those early issues as “…an experiment—an inquiry into the merits (and shortcomings?) of extreme specialization…”. Richard Freitag succeeded Willis in 1975, and that trio has edited and produced this “experiment”—now in its 41st year—ever since! Issues are available for a very nominal $10 per year ($13 outside of the U.S.). My sincere thanks to Artur Serrano (University of Lisbon) for permitting me to post his stunning photograph of the third-instar larva of Megacephala megacephala, photographed in Guinea-Bessau, Africa and gracing the cover of this latest issue.

Tetracha virginica in Wisconsin
Despite the common occurrence of this species across the southern two-thirds of the eastern U.S., its northern and western limits of distribution are still poorly known. Grimek discusses records of this species in Wisconsin during the 45-year period between 1962 to 2007, noting that all of the captures were from sandy areas near rivers in, with the exception of a single specimen, the “Driftless Area” covering the southwestern quadrant of the state. (The Driftless Area, also called the Paleozoic Plateau, is an area that escaped glaciation during the last glacial period). The capture of a specimen very near the Mississippi River suggests the species may also be found in Minnesota, where its occurrence has not yet been documented.

Grimek, H. 2009. Distribution of Tetracha virginica (Linnaeus) in Wisconsin. Cicindela 41(3):57-61

Brasiella cuyabaensis in Bolivia
Brasiella is a large genus (47 species) of small to very small, mostly Neotropical tiger beetles, of which B. argentata is among the most common and widespread. While examining specimens of this species that he had collected in Bolivia, Italian coleopterist Fabio Cassola found a second species among the material. At first thought to potentially represent a new species, its identity was ultimately revealed after examination of the unique male type specimen of B. cuyabaensis from Brazil. This specimen is very similar to B. argentata except for its genitalia (longer and narrower than in B. argentata), and Cassola has confirmed this in his material as well. The previously unknown females were especially problematic; however, Cassola found their longer, more convex labrum (upper lip) to be a useful diagnostic character. Cassola collected B. cuyabaensis some 700 km west of the type locality and speculates that additional specimens of the species may exist in entomological collections, incorrectly placed under B. argentata.

Cassola, F. 2009. Studies of tiger beetles. CLXXV. Occurrence in Bolivia of Brasiella cuyabaensis (Mandl, 1970) (Coleoptera: Cicindelidae). Cicindela 41(3):63-67.

DNA degrades rapidly in pinned tiger beetles
DNA molecular analyses are increasingly being used to elucidate relationships among tiger beetles, both at the species level and at higher levels of classification. However, such research is often hampered by the limited availability of sufficient fresh material representing less common taxa. Pinned museum specimens offer a potential source of DNA for such uncommon taxa; however, successful extraction of useable DNA from pinned specimens has been limited. Kritsky and Duennes, using a standardized DNA extraction method, determined that DNA extracted from pinned tiger beetles rapidly degrades during the first 25 years after collection before stabilizing at ~10% of the original DNA. The authors found that frozen specimens yeilded more DNA than specimens killed in ethanol, perhaps due to degradation of DNA by water in the ethanol, and noted that choice of killing method and use of fumigants during storage can also contribute to loss of DNA. More research is needed to determine optimal conditions for protecting museum specimens while preserving their DNA for future research.

Kritsky, G. and M. Duennes. 2009. The rate of DNA degradation in pinned tiger beetles. Cicindela 41(3):69-73.

Mississippi tiger beetles scavenge dead fish
An established breeding population of Cicindela pamphila [= Habroscelimorpha pamphila] was observed during 2006–2008 in a Mississippi coastal salt marsh. This species was previously considered a rare straggler into Mississippi, occurring primarily along the Texas Gulf Coast south into Mexico. The Mississippi population was observed co-occurring with C. hamata [= Ellipsoptera hamata], C. severa [= Habroscelimorpha severa], and C. togata [= Eunota togata]. On one occasion, individuals of C. hamata and C. severa were observed feeding on a fresh mullet (Mugil sp.) carcass resulting from a raptor kill, adding these two tiger beetle species to the list for which scavenging on dead vertebrates has now been confirmed. Despite the co-occurrence of four species of tiger beetles within this area, the author noted no apparent resource partioning and speculates that carrion resulting from predation by birds, racoons, etc. may provide a valuable resource for scavenging tiger beetles that reduces competition for food.

Grammer, G. L. 2009. A breeding population record of Cicindela pamphila in Mississippi and observations on the scavenging behavior of C. severa and C. hamata. Cicindela 41(3):75-80.

Florida Metallic Tiger Beetle

October 27, 2009October 10, 2011 / Ted C. MacRae / 22 Comments

Tetracha floridana (Florida Metallic Tiger Beetle), dorsal view

In my previous post, I showed some photographs of the larva of an undetermined species of tiger beetle that I collected from its burrow in dry ground adjacent to a coastal salt marsh near St. Petersburg, Florida. I had assumed the larva belonged to the genus Cicindela or one of its former subgenera and was suprised to learn that this assumption was incorrect when the adult emerged 2 months later. Looking back at the photos, however, I realized that the photos and the information I gave regarding its location and habitat contained all of the necessary information to identify this larva. Five points to Mike Baker, who correctly deduced the genus (Tetracha), and in fact the larva represents Tetracha floridana (Florida metallic tiger beetle).

Hump of 5th abdominal segment, showing simple, thorn-like inner and outer hooks

The hump of the 5th abdominal segment bears simple, thornlike hooks.

The larva can be placed in the genus Tetracha by virtue of its simple, thorn-like hooks (in other eastern U.S. tiger beetle genera, the outer hooks are distinctly curved). Two other genera of Nearctic tiger beetles that do not occur in Florida also bear simple hooks—Omus (Night-stalking Tiger Beetles, occurring along the Pacific Coast) and Amblychelia (Giant Tiger Beetles, occurring in the central and southwestern U.S.); however, the former bears three rather than two pairs of hooks, and the latter has the inner and outer hooks distinctly separated from each other.

Tetracha floridana (Florida Metallic Tiger Beetle), lateral view.

Four species of Tetracha occur in the U.S., three of which occur in Florida—T. carolina (Pan-American Big-headed Tiger Beetle), T. floridana (Florida Metallic Tiger Beetle), and T. virginica (Virginia Big-headed Tiger Beetle). However, T. carolina is restricted in the state to the panhandle and interior of the peninsula along rivers and in disturbed sparsely vegetated areas (Choate 2006). Of the two remaining species, T. virginica is widespread throughout the southern two-thirds of the eastern U.S. and occurs in a variety of habitats (Pearson et al. 2006), while T. floridana is restricted to salt marsh and mud flat habitats along the Gulf coast of Florida from Dixie County south to the Keys (Choate 2006). While the widespread occurrence and generalist tendencies of T. virginica might suggest that it is the more likely choice, the locality and habitat match precisely with T. floridana.

The anterior lobes of the apical lunules are divergent.

Tetracha floridana is very similar to T. carolina and was long considered a subspecies of that more widely distributed species until Naviaux (2007) elevated it to species rank in his revision of this large genus. Tetracha floridana is distinguished from T. carolina by the divergent anterior lobes of the apical lunules (photo above) and the uniformly black to dark green elytra that lack any violet or coppery reflections in the anteriolateral regions (photo below) (Choate 2003).

The anteriolateral areas of the elytra lack violet or copper reflections.

I was happy as heck when I saw the first newly emerged adult in the rearing container, as this is a true Florida endemic. I have encountered the two other eastern U.S. species commonly under street lamps and at building lights here in Missouri—T. virginica throughout the state and T. carolina in the southeastern lowlands, where it appears to reach its northern limit of distribution. A fourth U.S. species in the genus, T. impressa (Upland Metallic Tiger Beetle) (T. “affinis” in earlier works), occurs in northern Mexico and the Lower Rio Grande Valley (LRGV) of south Texas (Erwin and Pearson 2008). Although I have not yet encountered it on any of my many trips to the LRGV (all of which pre-date my current cicindelophily), I understand it is regularly attracted to building and street lights in Brownsville (Pearson et al. 2006). I believe I will have to go down there again and verify this for myself someday.

Feasting on a corn rootworm larva.

The last photo in this series illustrates the unique feeding behavior of these beetles, which despite their terrifyingly toothy mandibles are strictly fluid feeders. The long, sharp mandibular teeth function primarily in prey subdual and in slicing and shredding their tissues, while the maxillae (second pair of feeding appendages behind the mandibles) and labium (fused third pair of appendages) comprise an “oral mill” that masticates the prey and and rolls it into a bolus. Two brush-like structures can be seen behind the mandibles in the photo above—these are part of the maxillary laciniae and apparently function in containing and shaping the bolus as it is being masticated. While this occurs, proteolytic enzymes are extruded from the midgut and mixed with the bolus to liquify its digestible components, which are then sucked into the beetles tiny mouth by the action of a pharyngeal pump. Like the larva, the adult beetle thus “chews” but does not swallow its prey—a manner of feeding that is not too unlike that of spiders and other arachnids (sans the venom).

Photo details:
All photos: Canon EOS 50D, manual mode, ISO-100, 1/250 sec, MT-24EX flash w/ diffuser caps.
Photo 1: Canon 100mm macro lens w/ 68mm extension tube, f/25, 1/2 power flash.
Photo 2: Canon MP-E 65mm 1–5X macro lens, f/16, 1/8 power flash.
Photos 3–5: Canon 100mm macro lens w/ 36mm extension, f/18–f/22, 1/4 power flash.
Photo 6: Canon 100mm macro lens w/ 68mm extension, f/20, 1/2 power flash.

REFERENCES:

Choate, P. M., Jr. 2003. A Field Guide and Identification Manual for Florida and Eastern U.S. Tiger Beetles. University Press of Florida, Gainesville, 224 pp.

Choate, P. M., Jr. 2006. Tiger Beetles of Florida, Cicindela spp., Megacephala spp. (Insecta: Coleoptera: Cicindelidae). University of Florida, IFAS Extension Service Circular EENY-005, 5 pp.

Naviaux R. 2007. Tetracha (Coleoptera, Cicindelidae, Megacephalina): Revision du genre et descriptions de nouveaus taxons. Mémoires de la Société entomologique de France 7:1-197.

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.

Anatomy of a Tiger Beetle Larva

October 22, 2009October 10, 2011 / Ted C. MacRae / 13 Comments

My first experience looking for tiger beetles in Florida had gone well. Despite its small size and urban surroundings, the narrow strip of coastal scrub and saltwater marsh along the intracoastal waterway behind my sister-in-law’s condominium boasted a robust population of what I took to be a single tiger beetle species. The specimens I collected and photographs I took would later reveal that two co-occurring and closely related species were present: Ellipsoptera marginata (Margined Tiger Beetle) and E. hamata lacerata (Gulf Beach Tiger Beetle). I had spent close to two hours under the August sun observing and photographing the beetles before I decided that I had given the preserve a thorough enough look.

As I was heading back, I noticed a little bit of high ground alongside a red mangrove thicket and went over to give it a look. As I approached I saw something I hadn’t yet seen that day – tiger beetle larval burrows. Larval burrows, especially larger ones such as these were, are unmistakeable – almost perfectly circular (slightly cut out on one edge) and smoothly beveled around the perimeter. There were a number of burrows clustered on the small bit of high, dry ground, and my first thought was that their inhabitants represented the same (what I thought was a single) species that I had encountered so commonly that day as adults. I then reasoned, however, that more likely they represented another species whose adults are active later in the season – perhaps one of the so-called “spring/fall” species whose larvae typically reach maturity during the heat of summer. The size of the burrows (~5mm dia) suggested they were inhabited by 3rd instar larvae (the final instar before pupation), in which case it may be possible to rear a few to adulthood – if I could get at them. I tried fishing (Pearson and Vogler 2001) a few holes with a grass blade but didn’t get any bites, so I decided to watch for awhile and see if any of the larvae, believing the danger of my approach had passed, would reappear at the tops of their burrows. Waiting for tiger beetle larvae to appear is a crap shoot – maybe they’re active, and maybe they’re not, and crouching in the stifling summer air of a coastal marsh in Florida is not an easy thing to do for very long. Fortunately my wait was short, as within a few minutes I saw one re-appear at the top its burrow. I slowly got out my knife and moved to place the tip on the soil about 1″ from the burrow at a 45° angle for an attempted tunnel block (Pearson and Vogler 2001), but it spooked and dropped back down into its burrow before I could get then knife in place. No matter, I knew it was in there now and that it would likely reappear if I could muster the patience. I positioned the knife and waited – crouched under the baking Florida sun, until when it did re-appear I plunged the knife into the soil with authority. It was a good jab – I had blocked its retreat without injuring it, and a quick flip of the knife popped out the soil plug and exposed the startled larva, flipping vigorously in a vain attempt to escape before settling down amidst its unfamiliar, exposed surroundings.

For those of you who have never seen a tiger beetle larva, they are among the most other-wordly creatures one can imagine. The large, heavily sclerotized head bears two long, sickle-shaped, upward-pointing mandibles and up to three pair of highly-acute eyes whose arrangement on each side conveys the image of a “face” with congenital birth defects. The top of the head is flattened to lie flush with the surrounding soil as the larva sits at the top of its burrow, and huge, powerful mandibular muscles fill the cranial cavity. The remainder of the body – long, narrow, and cylindrical – hangs from the head at a 90° angle down into the burrow and is unremarkably grub-like, save for a curious hump on the dorsal side of the 5th abdominal segment. Close examination of the hump reveals an intricate pattern of forward-facing hooks and spines that function in anchoring the larva against the side of its burrow to prevent struggling prey from dislodging it. The life of a tiger beetle larva is a life of waiting – unlike the adults who run down their prey, the larvae sit in their burrows and wait for prey to come to within lunge’s reach. While the eyes of most grub-like insects detect little more than light and dark, those of tiger beetle larvae are densely packed with photoreceptors that permit detailed focusing and depth perception for detecting whether potential prey has ventured close enough to their burrow (Pearson et al. 2006). When that happens, they strike with lightning speed, plunge their mandibles into their prey, and drag it down into the depths of their burrow where it is summarily dispatched with a few bites of their powerful mandibles. Larvae consume they prey in a manner similar to that of adults in that they chew but don’t swallow their prey. Rather, they secrete digestive secretions containing proteolytic enzymes that begin digesting the prey extra-orally as they chew. The resulting bolus is masticated and its liquid components sucked out until nothing but a dry wad of indigestable chitin remains, which is spat out of the burrow (Pearson and Vogler 2001).

Looking at this strange insect, it occurred to me that I had not yet attempted macrophotographs of a tiger beetle larva out of its burrow, and this would be a good opportunity to get more practice with my Canon MP-E 65 mm macro lens – a lens with incredible magnification capabilities, but one that is also a bit of a temperamental beast to use hand-held in the field. The subject was unusually cooperative, perhaps too stunned by its sudden predicament to know what to do, and as I took the photographs I focused in particular on characters of the head and dorsal hump (often useful in identifying tiger beetle larvae, at least to genus). Time was growing short once I finished taking photographs, so I placed the larva in a vial and returned the following day to extract a chunk of native soil to place in a rearing container, managing to collect two more larvae as well (unfortunately, one became instant “prey” for the other. Note to self: when placing multiple tiger beetle larvae in a container of soil, seal the artificial burrows into which you place each one!). I paid little further attention to the photographs, other than to transfer them onto my computer and add metadata upon my return to St. Louis. I didn’t know what species the larvae represented, but I assumed they were something in the genus Cicindela or one of its several former subgenera. However, had I studied the photos and considered the locality and habitat, I would have realized that my assumption was incorrect¹. That realization would come in surprise fashion two months later when the two adults emerged within a few days of each other…

¹ Ten points to whoever can use this information to arrive at an identification before my next post 🙂

Photo details:
All photos: Canon EOS 50D, manual mode, ISO-100, 1/250 sec, MT-24EX flash w/ diffuser caps.
Photo 1: Canon 100mm macro lens, f/22, 1/4 power flash (photo slightly cropped).
Photos 2-4: Canon MP-E 65mm 1-5X macro lens f/16, 1/8 power flash.

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.

(My) Introduction to Florida Tiger Beetles

October 17, 2009October 10, 2011 / Ted C. MacRae / 26 Comments

On the last day of July, I hopped into my stuffed-to-the-brim SUV and began the +1000-mile drive to St. Petersburg, Florida. I had with me my camera and my collecting gear, but also my bike, some beach wear… and my family! No, this was not a collecting trip, but a family vacation. We would be staying at my sister-in-law’s condo with my niece and enjoying typical Florida vacation fare – beaches, Disney World, sightseeing. I even brought my road bike along to enjoy some pancake-flat terrain (a rarity around St. Louis) for a nice change of pace. Still, I can be rather single-minded when it comes to opportunities for bug collecting, and summer in Florida presents opportunities galore! Virtually everything there is different, and while I have been to Florida a number of times, my visits have all been during spring and prior to my more recent interest in tiger beetles. It would be a family vacation, but still I would find a way to sneak off a couple times and satisfy my compulsions, and while the girls talked about Disney World and the beach, visions of Cicindela abdominalis, C. highlandensis, C. scabrosa, Ellipsoptera gratiosa, E. hamata lacerata, E. hirtilabris, E. marginata, Habroscelimorpha dorsalis, H. severa, and H. striga danced through my head!

I wouldn’t have to go far to find my first Florida tiger beetles. My sister-in-law’s condo is in Seminole (west side of St. Petersburg peninsula), and as my niece and her husband showed us around after our arrival, they pointed out the “wild area” off their back patio next to the intertidal waterway and suggested, innocently, that I could go bug collecting back there. In such a developed urban/tourist area, I figured it must be highly disturbed, dominated by exotics, and offering little in the way of quality habitat for the serious bug collector. However, that night, as a cacophony of nasal queenks from the area made it clear that a healthy population of what I presume to be green treefrogs were thriving in the area, I reconsidered my skepticism and decided to take a quick look a day later. What I found was a small but high-quality strip of coastal scrub and saltwater marsh bordering the intracoastal waterway, with thickets of red mangrove (Rhizophora mangle) along the water’s edge, black mangrove (Avicennia germinans) “woodlands” in the high scrub areas, and moist, briney, barren ground in between (Photo 1). The whole area couldn’t have been more than a hundred yards wide but extended along the length of the waterway, and a wooden sign as I entered the area indicated it was a bona fide, albeit private, nature preserve established as part of the condominium development.

Intertidal salt marsh, Tara Cay Sound Nature Preserve, Seminole, Florida

Within minutes after entering the preserve I saw the first tiger beetle. I didn’t know what it was, and my first stalking efforts were woefully inadequate. I saw another one a few minutes later and got within net handle distance but muffed the swing. A few feet further along the path and onto an exposure by the water revealed several individuals, one of which I was finally able to capture after several clumsy misses. I hadn’t yet memorized key characters for all of the species I had the potential to encounter, but I could see in the hand that this individual almost certainly belonged to the genus Ellipsoptera (Ellipsed-winged Tiger Beetles) because of its resemblance to E. macra (Sandy Stream Tiger Beetle) and E. nevadica knausii (Knaus’ Tiger Beetle), which I had photographed earlier this year in Missouri and Oklahoma, respectively. With one now in the hand as a studio backup, I began my efforts to obtain field photographs. The beetles were extremely wary, with fast running and strong flight capabilities that made them very difficult to approach. It was only their abundance and my dogged persistance that allowed me to finally get close enough to one (Photo 2) to fire off a sequence of frames. I then spent some time collecting a voucher series – finally getting a beat on their behavior and able to capture them with a little more efficiency despite their ultra-wariness before concentrating on getting more photographs of different individuals (including those shown in Photos 3 and 4).

Ellipsoptera marginata - Margined Tiger Beetle

Ellipsoptera marginata - note "tooth" under right mandible of this male

Ellipsoptera marginata - another male, with a distinctly bronzed pronotum

Ellipsoptera hamata lacerata - Gulf Beach Tiger Beetle (mate guarding)

I returned to the condo after a couple of hours – completely drenched (remember, it was August in Florida!). When I had the chance to consult my “bible” (Pearson et al. 2006), I learned there there were two possibilities: Ellipsoptera marginata (Margined Tiger Beetle), occurring along the Atlantic seaboard from Maine to the Gulf coast of Florida; and Ellipsoptera hamata lacerata (Gulf Beach Tiger Beetle), resembling and closely related to E. marginata and occurring along the Gulf Coast from Florida to Texas. Both species inhabit coastal beaches, mud flats and salt marshes, and their distributions overlap along Florida’s Gulf Coast. While they are easily distinguished from other species in the genus by the distinctively diffuse middle band of the elytra, distinguishing between the two requires examination of the male right mandible (marginata bears a distinct tooth on the underside, hamata does not) or female elytral apices (marginata curiously bent down at a 90º angle, hamata not). At this point, I didn’t know if I had one species or two – and if I did have two, did I have photographs of both (and would I be able to identify them)?

Fortunately, closer examination of the voucher series I collected revealed both species present, and even more fortunately I had managed to get photographs of both. The individual in Photo 2 is a male, and the angle of the photograph clearly reveals a distinct tooth on the underside of the right mandible, identifying it as E. marginata. Photo 3 is another male, and although the angle doesn’t afford a view of the mandibles, what can be seen is a bronze cast to the pronotum – in my voucher series, all of the E. marginata specimens have a bronze cast to the pronotum, while the E. hamata lacerata specimens exhibit an olive cast. This suggests that this individual also represents E. marginata. In Photo 4, no tooth can be seen on the male mandible, but the angle of the photo doesn’t necessarily make it visible were it to exist. The male does, however, exhibit an olive cast on the pronotum, and the female elytral apices show no indication of being bent down as would be expected for E. marginata (see Photo 5 below of E. marginata photographed a few days later at another locality). As a result, the individuals in Photo 4 can be identified as E. hamata lacerata.

Ellipsoptera marginata - female elytral apices showing curiously "bent tips"

Of the 19 vouchers that I collected, 15 represent E. marginata and 4 represent E. hamata lacerata. This exemplifies the challenges of field identification and photography of insect species in unfamiliar places. Had I been satisfied with photographing only one or two individuals of what I thought were all the same species, I would have missed one of the species. The experience further exemplifies the importance of adequate voucher series, as it was only a result of close examination of that series that I realized two species were present. Based on the numbers of individuals that I collected, as well as the photographs that I took, it appears that E. hamata lacerata was much less common at that location than E. marginata. This difference in population density between two similar, co-occurring species emphasizes the importance of sampling an adequate number of individuals at a given location before concluding what species are – and are not – present.

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.

Cold and wet

October 13, 2009October 10, 2011 / Ted C. MacRae / 12 Comments

Photo details: Canon 65mm 1-5X macro lens on Canon EOS 50D, manual mode, ISO-100, 1/250 sec, f/14, MT-24EX flash 1/8 power through diffuser caps.

Photo details: Canon 65mm 1-5X macro lens on Canon EOS 50D, manual mode, ISO-100, 1/250 sec, f/14, MT-24EX flash 1/8 power w/ diffuser caps

The annual fall tiger beetle collecting trip is over, and nothing could be more emblematic of the trip than this cold, wet Cicindela splendida (literally translating to its well-deserved common name “Splendid Tiger Beetle”), found in the waning light of the last day of the trip secreted under a rock in the dolomite glades at White River Balds Natural Area in southwestern Missouri. Overcast skies and a cold, stiff breeze had already dashed my hopes of finding Cicindela pulchra (also translating to its equally well-deserved common name “Beautiful Tiger Beetle”) in the Red Hills of northwestern Oklahoma two days earlier, and these same unrelenting conditions thwarted my backup plans to find this species the next day in the Gypsym Hills of nearby Barber County, Kansas. With one last day to spend in the field, I had worked my way back to the White River Hills in hopes of photographing Missouri’s disjunct population of the enormous Cicindela obsoleta vulturina (Prairie Tiger Beetle). That would also not come to pass, as the sun’s efforts to burn through the thick cloud cover just weren’t quite enough. By the end of the day, I had resorted to flipping rocks (and replacing them exactly, of course) in hopes of finding an individual or two still in their nighttime/cool weather roosts. I had seen C. obsoleta on previous occasions at this very locality along this very trail, but this time none were found – my finds instead limited to the “smiling” scorpion that I featured a few days ago and this lone C. splendida – wet with condensation and torpid against the cold ground. I hatched a last gasp plan to look for C. obsoleta again the following day before heading back to St. Louis, but I awoke the next morning to steady rain and knew the 2009 entomology field season was officially over.

Don’t let me leave you with the impression, however, that the trip was a failure. While I didn’t find either of the two species that I had set as my top goals for the trip, I still saw enough new things to make the trip worthwhile (including one very significant find that I’ll discuss in an upcoming post). In addition, I’ve barely made mention of my August trip to Florida – my Assasin ate post of a couple weeks ago was just one of many interesting finds encountered during that trip that remain to be shared. The cold and rain that has settled over the middle of the country during the past week have brought an unwelcome end to my field work for the year, but that just leaves me with more time now to process and share photographs from the past season and reflect on the stories behind them. It will be welcome diversion, as I also begin the arduous and seemingly endless task of mounting and labeling the specimens collected during the past season – success’ bitter reward!

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Beetles In The Bush

Experiences and reflections of a Missouri entomologist

Cicindelidae

A “Really” Big-headed Tiger Beetle

Moustached Tiger Beetle

Highlands Tiger Beetle

Beetle Research Roundup

Florida Metallic Tiger Beetle

Anatomy of a Tiger Beetle Larva

(My) Introduction to Florida Tiger Beetles

Cold and wet

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