Predator or Prey?

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.


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

Bichos Argentinos #10 – Friday Formicine

One of the insects I saw abundantly during my visit last month to La Reserva Ecológica Costanera Sur (Buenos Aires, Argentina) was this species of black ant that looks well enough like one of our typical North American species. They were quite common, seen on virtually every plant that I examined closely. I made a few feeble attempts at photographs in the early part of the day, but desire faded quickly in the face of their frenetic behavior and occurrence in exclusively tough-to-photograph situations.  I mean, they’re just ants!¹ Around midday I noticed that many of the flower heads of the pampas grass clumps in the area had at least one ant perched in this interesting head-down, abdomen-curled forward position – I tried to capture the situation, but even this best of the bunch turned out, well… boring!

¹ Just kidding Alex and James!

Finally, late in the day, I saw one crawling on the trunk of a recently fire-killed tree that I was inspecting in (futile) hopes of encountering adult jewel beetles or longhorned beetles that would have been attracted to this newly available resource.  This was the easy-to-photograph situation I was waiting for, and the dark color of the charred bark brought out nicely the hairs on the body despite both ant and bark being nearly the same color.

I’m a beetle guy, and normally I would be happy to just call this Formica nigra and move on.  Whatever possessed me to even begin the process of trying to identify this particular ant is beyond me (maybe I’ve actually learned something after a couple of years of reading Myrmecos!).  It had the look of our North American Camponotus, so I entered “Camponotus Argentina” into Google Images and found this photo of Camponotus mus, taken by our friend Alex in nearby Santa Fe, Argentina, near the top of the very first page.  Now, I realize that closely (and even distantly) related species can look quite similar (especially to the untrained eye), but everything about this ant looks right – the bulbous-abdomen, the shape of the thorax, the matt black color, and the velvety yellowish pilosity of the abdomen. A little searching on the name reveals this species to be quite abundant in Argentina, where it goes by the common names “hormiga de madera” (wood ant) and, not surprisingly, “hormiga carpintera” (carpenter ant). Alex? James? Did I get it right?

Copyright © Ted C. MacRae 2011

Bichos Argentinos #2 – Pseudomyrmex sp.

Pseudomyrmex sp. (twig ant) | Reserva Ecológica Costanera Sur, Buenos Aires, Argentina

One of the insects I tracked at La Reserva Ecológica Costanera Sur in Buenos Aires, Argentina last weekend was this twig ant in the genus Pseudomyrmex.  I had noticed these slender, wasp-like ants previously on trips to the U.S. desert southwest, but it wasn’t until I read a couple of recent posts about them at Myrmecos and 6legs2many that I knew specifically what they were. 

Alex characterizes these ants as “delightfully gentle, quirky little insects.”  What he didn’t mention is how frenetic and unceasing they are as they forage amongst the shrubbery.  I must have taken a couple dozen shots of several individuals over the course of the day, deleting every single one on the spot because I couldn’t get a clear, close, focused, nicely composed, unobstructed image.  Their habit of crawling rapidly along slender twigs is problematic enough, with little opportunity to brace the camera against anything steady and spend time composing the shot.  Add to that the frequently thorny nature of the trees they were roaming and their annoying habit of darting around to the backside of whatever twig they were on whilst trying to follow them in the viewfinder, and I almost decided I’d met my match and could do without the shot.  In the latter part of the day I encountered this individual, and as I already had my 65mm lens mounted I decided to give it another try.  I can’t say that I actually figured out the secret to getting the shot, but rather that I just lucked out and happened to have hit the shutter release at just the right moment – and with reasonable focus – as I tracked the ant along the branch on which it was crawling.  It was the only shot of one of these ants that stayed on the card that day.

The genus is huge, with 209 species occurring primarily throughout the Neotropics.  As a result, it would be foolish for me to even attempt a species ID.  Still, I can’t help noticing its great resemblance to this photo of Pseudomyrmex phyllophilus, taken by Alex in – you guessed it, Buenos Aires, Argentina.  I’ll wait for the correction, but in the off-chance that I’m right I think I deserve points on somebody’s scorecard!

Copyright © Ted C. MacRae 2011

Brazil Bugs #15 – Formiga-membracídeos mutualismo

Of the several insect groups that I most wanted to see and photograph during my trip to Brazil a few weeks ago, treehoppers were near the top of the list.  To say that treehoppers are diverse in the Neotropics is certainly an understatement – South America boasts an extraordinary number of bizarre and beautiful forms that still, to this day, leave evolutionary biologists scratching their heads.  The development of this amazing diversity is a relatively recent phenomenon (thinking geological scale here), as there are no known membracid fossils prior to Oligo-Miocene Dominican and Mexican amber – well after the early Cretaceous breakup of Gondwanaland split the globe into the “Old” and “New” Worlds.  With its origins apparently in South America, numerous groups continued to spring forth – each with more ridiculous pronotal modifications than the last and giving rise to the dazzling diversity of forms we see today.  Even North America got in the evolutionary act, benefiting from northern dispersal from South America’s richly developing fauna via temporary land bridges or island stepping stones that have existed at various times during the current era and giving rise to the almost exclusively Nearctic tribe Smiliini (whose species are largely associated with the continent’s eastern hardwood forests).  Only the subfamily Centrotinae, with its relatively unadorned pronotum, managed to successfully disperse to the Old World, where it remains the sole representative taxon in that hemisphere.  With a few notable exceptions, treehoppers have virtually no economic importance whatsoever, yet they enjoy relatively active study by taxonomists, evolutionists, and ecologists alike – due almost completely to the bizarreness of their forms and unique mutualistic/subsocial behaviors.

I did manage to find a few species of treehoppers during the trip (a very primitive species being featured in Answer to ID Challenge #4 – Aetalion reticulatum), and of those that I did find the nymphs in this ant-tended aggregation on a small tree in the rural outskirts of Campinas (São Paulo State) were perhaps the most striking in coloration and form.  Most were jet black, although a few exhibited fair amounts of reddish coloration, and all exhibited sharply defined white bands of wax and long erect processes on the pronotum, mesonotum, and abdomen.  I’ve seen a fair number of treehopper nymphs, but I did not recognize these as something I had seen before, and given the incomplete state of immature taxomony I feared an identification might not be possible.  Still (and I know this is probably beginning to sound like a broken record), I gave it the old college try.

I usually like to start simple and get more creative if the results aren’t satisfactory, so I went to my old friend Flickr and simply typed “Membracidae” as my search term.  Predictably, pages and pages of results appeared, and I began scanning through them to see if any contained nymphs at all resembling what I had.  After just a few pages, I encountered this photo with very similar-looking nymphs, and although no identification beyond family was indicated for the photo, I recognized the lone adult sitting with the nymphs as a member of the tribe Aconophorini – a diverse group distinguished from other treehoppers by their long, forward-projecting pronotal horn.  Luck was with me, because I happen to have a copy of the relatively recent revision of this tribe by Dietrich and Deitz (1991).  Scanning through the work, I learned that the tribe is comprised of 51 species assigned to three genera: Guayaquila (22 spp.), Calloconophora (16 spp.), and Aconophora (13 spp.).  The latter two genera can immediately be dismissed, as ant-interactions have not been recorded for any of the species in those two genera – clearly the individuals that I photographed were being tended by ants.  Further, the long, laterally directed apical processes of the pronotal horn, two pairs of abdominal spines, and other features also agree with the characters given for nymphs of the genus Guayaquila.  In looking at the species included in the genus, a drawing of a nymph that looked strikingly similar to mine was found in the species treatment for G. gracilicornis.  While that species is recorded only from Central America and northern South America, it was noted that nymphs of this species closely resemble those of the much more widely distributed G. xiphias, differing by their generally paler coloration.  My individuals are anything but pale, and reading through the description of the late-instar nymph of the latter species found every character in agreement.  A quick search of the species in Google Images was all that was needed to confirm the ID (at least to my satisfaction). 

In a study of aggregations of G. xiphias on the shrub Didymopanax vinosum (Araliaceae) in southeastern Brazil, Del-Claro and Oliveira (1999) found an astounding 21 species of associated ant species – a far greater diversity than that reported for any other ant-treehopper system.  The most frequently encountered ant species were Ectatomma edentatum, Camponotus rufipes, C. crassus, and C. renggeri, and after perusing the images of these four species at AntWeb I’m inclined to believe that the ants in these photos represent Camponotus crassus (although I am less confident of this ID than the treehoppers – corrections welcome!).  The authors noted turnover of ant species throughout the day in a significant portion of the treehopper aggregations that they observed, which they suggest probably reflects distinct humidity and temperature tolerances among the different ant species and that might serve to reduce interspecific competition among ants at treehopper aggregations.  Since treehopper predation and parasitism in the absence of ant mutualists can be severe, the development of multispecies associations by G. xiphias results in nearly “round-the-clock” protection that can greatly enhance their survival.

Update 3/3/11, 9:45 a.m.:  My thanks to Chris Dietrich at the Illinois Natural History Survey, who provided me in an email exchange some clarifying comments on the origins and subsequent dispersal of the family.  The first paragraph has been slightly modified to reflect those comments.


Del-Claro, K. and P. S. Oliveira. 1999. Ant-Homoptera interactions in a Neotropicai savanna: The honeydew-producing treehopper, Guayaquila xiphias (Membracidae), and its associated ant fauna on Didymopanax vinosum (Araliaceae). Biotropica 31(1):135–144.

Dietrich, C. H. and L. L. Deitz.  1991.  Revision of the Neotropical treehopper tribe Aconophorini (Homoptera: Membracidae).  North Carolina Agricultural Research Service Technical Bulletin 293, 134 pp.

Copyright © Ted C. MacRae 2011

Brazil Bugs #11 – Formigas cortadeiras

This week is Army Ant Week, and while Alex Wild’s stunning photographs of this diverse and charismatic group reign supreme, some of the cooler bug bloggers are nevertheless getting into the spirit of things with army ant posts of their own.  I have no such photos, but I’m hoping I can sneak onto the bandwagon with these images of leafcutting ants that I photographed last month in Campinas, Brazil.

These were among the first insects I saw during the trip once I got a bit of free time to walk the hotel grounds.  Watching them crawl along the lower edge of the hotel wall was a welcome sight, as nothing says “tropics” to me more than columns of these ants carrying their bits of leaves back to the nest for use in their hidden fungus farms.  While taxonomically they may be unrelated to army ants, their precise single file marches in dutiful service to the colony are as military as it gets.  Army ants may have the jaws, but leaf-cutters have spines – they don’t just carry weapons, they are the weapons!

The thing I like most about leaf-cutter ants is that they are one of the few ant groups that I feel confident enough to hazard an attempt at identification.  Several genera comprise the group, and most people who are at all familiar with them think of the genus Atta first.  However, I recalled reading something on Alex’s blog about spines as a diagnostic character for attine ant genera – sure enough, in this post Alex explains how species in the genus Atta have two pairs of spines on the promesonotum, while those in the genus Acromyrmex bear three pairs.  On this basis, I’ll go out on a limb and declare the individuals in these photos as Acromyrmex sp. (of course, which species is another story – James?  Alex?).  If I’m proved right, it will confirm the worthwhileness of all my blog trolling.  If I am wrong – well, there’s still nothing wrong with idle entertainment.

Copyright © Ted C. MacRae 2011

Brazil Bugs #9 – Formiga hostil

I found this ant crawling over the blossoms of the Ixora shrubs on the grounds of my hotel in Campinas (São Paulo state). Normally I wouldn’t even try to identify a South American ant, but the individual quickly and easily keyed out in the recent revision of North American Formicidae to Formica nigra – apparently a very wide-ranging species!¹

¹ Seriously, I would welcome input from any myrmecophiles out there on the actual identity of this species.

As I started taking some photographs, she seemed to take note of my presence.
With each shot, she seemed to become increasingly more irritated.
Irritation soon gave way to outright hostility.
In short order, the meaning was all too clear – “Stay away from my flower!”
Copyright © Ted C. MacRae 2011

Revision of the Formicidae of North America

Formica meganigra guarding a nest entrance.

I recently came across this ant in the southeastern Missouri Ozarks sitting in a hole in the trunk of a standing dead black oak (Quercus velutinus) tree, apparently guarding the entrance to its nest. This big black ant is frequently associated with dead wood; however, this is the first time I’ve noticed one guarding the entrance to its nest. Other workers coming back to the nest were greeted by this individual by a quick rubbing of antennae and then allowed to pass. The close approach of my camera apparently was not very welcome by the ant, who responded by showing off his *her* impressive choppers.

In trying to determine the species name for this ant, it became clear to me that myrmecologists have made things far more complicated than they really need to be. When I was a kid, ant identification was easy – there were black ants and red ants, and within those two main guilds some were big, some were not so big, and some were really small.  Peter Yeeles alluded to this traditional classification in a recent comment at Fall to Climb, which the Geek herself later modified to recognize ants that were neither black nor red.  In that classification, this is clearly a big black ant; however, the myrmecologists have unnecessarily split this species up into multiple genera and species based on inconsequential characters such as punctures on the head, clypeal notches, hairy scapes, etc.  I propose to bring a measure of sanity back to ant identification in North America with a revised key to the family (below).  It is based on the traditional classification but also recognizes the introduction in recent years of an alien species that stings and has colonized a large part of the southern United States (we didn’t have those when I was a kid).  In offering this simplified classification, it is my hope that school children across the country – naturally curious about ants and other insects – will no longer have their budding interest squashed by the ponderous, complex ant identification system that has become so fashionable in recent years.

Photo Details: Canon MP-E 65mm 1-5X macro lens on Canon 50D, ISO 100, 1/250 sec, f/14, MT-24EX flash 1/8 power w/ Sto-Fen diffusers.

Revised Key to Formicidae of North America

1 Color black . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1′ Color not black . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 (1) Enormous. . . . . . . . . . . . . . . . . . . . . . Formica meganigra (big black ant)
2′ Not enormous. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3 (2′) Regular size . . . . . . . . . . . . . . . . . . . . . . . . . . . Formica nigra (black ant)
3′ Tiny. . . . . . . . . . . . . . . . . . . . . . . . . . Formica micronigra (little black ant)
4 (1′) Color red. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4′ Color yellow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5 (4) Can sting. . . . . . . . . . . . . . . . . . . . . . . . . . . . Solenopsis invicta (fire ant)
5′ Can’t sting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Formica rubra (red ant)
6 (4′) Regular size. . . . . . . . . . . . . . . . . . . . . . . . . . . Formica flava (yellow ant)
6′ Tiny . . . . . . . . . . . . . . . . . . . . . . . . . Formica microflava (little yellow ant)

Copyright © Ted C. MacRae 2010

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Pismire Puzzle

I returned home from a much-needed vacation late last night, and even though it was a family trip I have much to share from the past 10 days. However, I must remain coy about where I was for the time being so that I may present this little quiz:

Who am I?

I had planned to post this yesterday, but the best title I could come up with – “Monday Myrmecine Mystery” – was just too similar to a Monday tradition on another blog that we’ve all grown to love.  (Also, I just couldn’t get to it.)  No longer constrained by an M-themed title, I came up with this alternative¹ that I hope will make the 12-year old boy in each of us giggle aloud.

¹ Pismire (from pissemire) is an archaic name of Scandinavian origin for ant. Derived from pisse urine (referring to the smell of formic acid) + mire ant.

What am I doing?

I expect members of the Formicine Guild will jump all over this, so I should probably make this quiz about more than just the name of the ant (which I don’t know, so does that make this an illegal quiz?).  Maybe I should offer double points to non-myrmecologists for a proper ID (but then, I would need the consensus of the myrmecologists – perhaps a conflict of interest?).

Why do I do this?

I could also offer points for correctly guessing what the ant is carrying – which again I wasn’t able to figure out, so I guess points will have to be awarded for the most plausible explanation.  What I do know is the ant carried this carcass while meandering aimlessly over the same patch of ground – occasionally stopping very briefly to dig its jaws into it before resuming its wanderings.  I followed the ant for about 10 minutes, and it never left an area of about 1 square foot – no nest nearby that I could see, no direction to its travels, no apparent purpose to its labors.

This is where I live.

I most definitely know where I was, so firm points are on offer for correctly guessing the answer to that question – either on the basis of the ant ID or the above photograph of its habitat.  Yes, that is snow on the ground – lots of it!

Copyright © Ted C. MacRae 2010

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