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).
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.
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.
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).
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.
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).
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.
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.
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.
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.
Copyright © Ted C. MacRae 2009
22 thoughts on “Florida Metallic Tiger Beetle”
Exceptionally impressive photos! This is a marvelous creature, and you captured that well. Though I’ll admit I never would have come close to identifying it from the larva–at least not without a great deal more study and research. Call me a generalist in such matters.
I was especially intrigued by the whole chew-it-until-you-can-drink-it thing. Different from arachnids, yet somehow similar.
Exceptionally kind remark! Thanks. The ID quiz was definitely one for the specialists.
There’s just something ironic about a vicious predator with huge, jagged mandibles that drinks its meals through a straw.
What a gorgeous beetle Ted. You have the best adventures, I need to go on my insect hunting/ photography explorations 😮
I always learn so much visiting here, thanks for all the hard work u put into your posts.
Thanks, Shelly, but you must remember that I’ve been at this for a long time – accumulated experience really increases one’s chances of “stumbling” into something. I thank you for your interest.
Hi Ted – this is the first time I have had a really good look at a Tiger Beetle. Wow – great green color, and I love the blue-ish eyes.
You said, “the adult beetle thus “chews” but does not swallow” – which I thought was funny because sometimes I swallow without chewing. 🙂
I attended an Introduction to Insects class this past weekend at the annual meeting of the Texas Master Naturalists. It was fascinating. One of the entomologists mentioned that some people specialize in collecting Tiger Beetles because of their beauty, and I thought, “Yep, I know one of those guys.”
Who was the entomologist?
I should mention that, their beauty notwithstanding, I find tiger beetles of interest more for their penchant for extreme habitats, their extraordinary polytopic variability, and the challenge they present to those interested in finding, photographing, and collecting them. They’re toothy-jawed predators with a boatload of behavioral idiosyncracies – that’s charisma! Add to that their beauty, and it’s a group that has it all!
Ok, now I’m going to have to start looking for Tiger Beetles too! They had me at “pretty,” but now I’m really impressed.
There were two entomologists, and I can remember the name of one without checking my notes – his name is Michael Merchant of the Texas A&M University’s Department of Entomology. His colleague also works with Texas A&M but I’ll have to look up his name.
Well, I’m glad to hear we’re gaining another convert. Birds, bugs, beetles… they’re all spectacular in some way.
Excellent – I love getting to see photos of larva. Especially tigers. Throw in a break down of ID by hump hooks & I’m ever so happy. Thanks.
(Incidentally, I spent three years working on a beach that was just fracking full of tigers & never once found an inhabited burrow on my lunch break. The adults are fast but the babies are sneaky.)
Hi Emily – glad you liked it. Larval burrows are often not quite in the same place as where the adults are found. Also, my impression is that they only spend a small portion of their time actually waiting at the burrow entrance. I’ve noticed that when I find a group of burrows, if I just stand there silent and watch for a while, eventually one will pop back up to the entrance. Moving into position to try to get it almost always causes it to drop back down, but if you’re really patient (hard when it’s 90 degrees and mosquitoes are biting!) it will come back up after some minutes.
P.s. What does a pharyngeal pump look like?
The pharyngeal pump is just a big muscle in the throat attached to the esophagus. Contraction of the pharygeal muscle causes the esophagus to expand, resulting in negative pressure that sucks in liquid through the small esophageal orifice. The pharygeal pump can be most easily visualized in the huge clypeaus of the cicada, which is the external covering of the pharygeal muscle. The striations on its surface represent internal ridges for muscle attachment.
There’s a peerless allure to insects shouldering such large, cumbersome mouthparts. What more can I say — the sixth photograph is spectacular!
Those really are awesome mouthparts, aren’t they? Thanks!
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I was looking for some information on these metallic tiger beetles, I am in texas and I have been seeing them for the last month so I looked them up to find out what type of beetle it was, before I found out I called them zoomy bugs because they zoom around our patio.. I only see one at a time but I think I found out where they are staying to. Any input?
This species lives only in Florida, but there are related species in Texas. I can’t really comment without knowing which one you are seeing, and if indeed it really is one of these beetles.
I too live in Texas, near Galveston bay, and caught one of these fast critters running through my office building. I have a couple pictures I’d like to share, if that can help identify which type of Tiger beetle it is. My daughter is doing an insect collection as a summer activity, but we like to keep them alive. Any tips on feeding or habitat for release?
Hi Amy – you may have the Carolina metallic tiger beetle («Tetracha carolina») if it looks similar to the Florida metallic. If you’d like to send pics for verification, you can send me an email (link above) and then attach the pics to my reply. Tiger beetles are easy to keep in captivity. You can feed them small insects captured locally or purchase mall crickets at a pet store.
Here are the two pictures I have. We are a little worried about him… But I do believe he’s nocturnal. He was very busy early this morning but not now… At 8:30am. If you can tell us what type he is and how we should build his habitat, it would be greatly appreciated. I hope the pictures attach correctly. If not then you may have to spell out your email address so I can try again. Thank you so much for your time. By the way… There are no small local insects…. We are in Texas! LOL. Everything is HUGE here. I’m going to send the pics separately. I’m not sure how to attach them here. Amy
Sent from my iPhone