Mutillidae

Velvet ants, cow killers. About 5,000 species. Larvae develop as primary external parasites of ground-nesting insects. Females wingless, spending large proportion of time underground; known for their extremely painful sting.

Party on a pin oak

/ Ted C. MacRae / 9 Comments

In September 2012 while collecting in western Oklahoma (Weatherford) I came across this interesting scene. It had been exceedingly dry in the area, and because of this few insects were out and about in the small city park that I stopped by to check for the presence of tiger beetles. I had nearly completed my circuit of the park when I came upon a moderate-sized pin oak (Quercus palustris) tree and noticed something on the lower trunk:

Six insect species representing five families in four orders share a sap flow.

Six insect species representing five families in four orders share a sap flow on the trunk of a pin oak.

No less than six insect species representing four orders were seen all huddled together at a darkly stained sap flow. This could be the result of slime flux, a bacterial disease that usually affects deciduous hardwoods that are under stress and results in darkly stained weeps on the trunk that are known to be attractive to a variety of insects. At the center sat a green June beetle (Cotinis nitida) and three bumble flower beetles (Euphoria inda)—all in the family Scarabaeidae (subfamily Cetoniinae). Covering the scarab beetles were half a dozen Texas Tawny Emperor (Asterocampa clyton texana) butterflies (family Nymphalidae, or Brushfooted Butterflies), and milling around the perimeter was a velvet ant (Dasymutilla creusa, I believe) in the family Mutillidae, an apparent flesh fly (family Sarcophagidae), and a true ant (family Formicidae). I guess this would be the equivalent to a watering hole in Africa with a lion, a hyena, a baboon, three vervet monkeys and six zebras all crouched shoulder-to-shoulder at its edge.

Euphoria sepulchralis feeds on a sap flow higher up on the trunk.

Euphoria sepulchralis feeds on a sap flow higher up on the trunk.

Further up on the trunk, yet another species of scarab beetle, a dark flower scarab (Euphoria sepulchralis) was found feeding on a smaller sap ooze. Unlike the diverse aggregation of insects on the lower ooze, this guy had managed to keep the ooze all to himself.

Cotinus nitidus | Weatherford, Oklahoma

Cotinis nitida | Weatherford, Oklahoma

Green June beetles, especially, are known for their feeding on sap oozes. The beetles are actually attracted to the odors caused by fermentation of the sap rather than the sap itself. It has been reported that the presence of alcohol in fermenting sap can affect the behaviour of insects that feed upon it, causing them to act “stupid and lethargic.” I did not see any such behavior, but I did notice that the insects were not at all skittish and loath to leave the sap.

Copyright © Ted C. MacRae 2013

The gloriously dichromatic Dasymutilla gloriosa

/ Ted C. MacRae / 3 Comments

I have a small collection of velvet ants (family Mutillidae) that I’ve accumulated over the years—not through active collection but more as bycatch from my beetle hunting operations. Velvet ants are, of course, not ants at all, but wasps, and as such the females are—like their winged relatives—quite capable of delivering a painful sting if mishandled. They also tend to be seen running rather frenetically across the ground, making them difficult to guide into a collection vial or grab with forceps. You’ve gotta really want ’em if you want to collect them. Still, even though I don’t study them I find them interesting enough to pick up on occasion, and with most groups outside of my area of focus the hope is that eventually they will end up in the hands of somebody who actively studies the group. Such is now the case with my mutillid collection, which will be shipped this week to another collector specializing in the group. In return I will be filling some holes in European representation of my collection of Cerambycidae.

Dasymutilla gloriosa, female | Brewster Co., Texas

Dasymutilla gloriosa, female | Brewster Co., Texas

Without question, the most interesting mutillid species that I’ve encountered is Dasymutilla gloriosa. All mutillids are sexually dimorphic, as only the males are winged, but most also tend to be sexually dichromatic to a greater or lesser degree. No species I am aware of takes this to the same level as D. gloriosa! The males (photo below) are rather typically colored compared to other species in the genus, but the females (photo above) are densely covered with long, strikingly white hairs. While this would seem to make them quite conspicuous, the true effect is the exact opposite as they easily confused with fuzzy plant seed. For this reason they are commonly called thistledown velvet ants. I encountered the female in west Texas in 2003 while walking a mountain trail and at first thought it was the fuzzy seed of a creosote bush (Larrea tridentata) being blown by the wind—except there was no wind! It took me a little while looking closely at it before I could figure out what it actually was. This is the only female of this species that I’ve seen in the wild, and I’ll be a little sad to see it sent to another location.

Dasymutilla gloriosa, male | Riverside Co., California

Dasymutilla gloriosa, male | Riverside Co., California

The male also is the only one I’ve encountered—or at least taken the trouble to collect. I would have never suspected this male, which I collected in southern California in 1991, was the same species as the female that I collected many years later. My thanks to Kevin Williams, who provided the identifications for both of these specimens.

Also called the ''thistledown velvet ant''

Also called the ”thistledown velvet ant”

Copyright © Ted C. MacRae 2012

Maddening mutillid

/ Ted C. MacRae / 7 Comments

Traumatomutilla graphica (Gerstaecker, 1874) | Parque Nacional Chaco, Argentina

During my stay in Corrientes, Argentina, I had two distinct biomes to explore—the relatively moist “Selva Paraguayense” to the east in Corrientes Province (a southern adjunct to the Atlantic Forest of southeastern Brazil, and home to the cryptic longhorned beetle that I featured in Desmiphora hirticollis: Crypsis or Mimicry?), and the drier “Gran Chaco” to the west, home of the insect featured in today’s post. Precious few remnants remain of the original Gran Chaco, which once covered nearly 1 million square kilometers in northern Argentina, Paraguay and Bolivia and the best example of which can be found at Parque Nacional Chaco in north-central Argentina. I’ve already mentioned that conditions are typically quite dry by early April in northern Argentina, and this is especially true of Chaco Province, where droughts during the months of January through March are common. As a result, I didn’t expect to see much insect activity during my visit last month. For the most part this was true, but one insect I did see at several points along the trails through the park was this rather large velvet ant (order Hymenoptera, family Mutillidae). Not an ant, of course, but a true wasp, these insects must be treated with respect as they are capable of delivering a painful sting. This, combined with their ceaseless, erratic wanderings makes them incredibly difficult to photograph. However, with few other insects to see, I thought I would spend the time and effort to see if I could get some good field photographs of this very attractive species. I spent about half an hour attempting to photograph it by panning through the viewfinder while getting closer and adjusting the focus on the move, and then firing shots when I thought I might be close enough and had the individual more-or-less within the frame. This was wildly unsuccessful, as I had only a 3-ft wide path within which to work and had to constantly get up to block its escape into the adjacent vegetation. Moreover, it was exhausting! The constant moving and body contortions while in crouched or kneeling positions used muscles I didn’t even know I had (but was well aware of the following day by their soreness!). Out of the countless shots that I fired, these two photographs are the only ones that I consider worthy of posting—pretty good, but not great.

The distinctive color pattern is diagnostic for the species.

According to Kevin Williams (many thanks!), the distinctive color pattern readily identifies this individual as Traumatomutilla graphica (Gerstaecker, 1874). Nearly the size of our common eastern North American Dasymutilla occidentalis (a.k.a., cow killer), the bold, conspicuous patterning surely must serve as advertisement of its powerful defensive capabilities—I know I was deterred from trying to handle it. Kevin mentions it as a “great find!” and that the male of the species is still unknown, and I could find nothing about the biology of this species. However, mutillids in general are known to develop as external parasitoids of various wasps, bees, beetles and flies, the excessively long female ovipositor enabling piercing of host nest cells before injecting their powerful venom and placing the eggs (Hogue 1993).

REFERENCE:

Hogue, C. L. 1993. Latin American Insects and Entomology. University of California Press, Berkeley and Los Angeles, 536 pp.

Copyright © Ted C. MacRae 2012

Pseudomethoca simillima – a model for Enoclerus ichneumoneus?

/ Ted C. MacRae / 18 Comments

Pseudomethoca simillima (family Mutillidae) - the model?

Enoclerus ichneumoneus (family Cleridae) - the mimic?

Last week, I posted the above photograph of Enoclerus ichneumoneus (orange-banded checkered beetle) and mentioned its possibly mimetic appearance to velvet ants in the family Mutillidae (order Hymenoptera).  By some stroke of serendipity, I encountered a species of Mutillidae the very next day in Missouri’s southeastern lowlands that seems to be a good candidate for one of, if not the, model species that E. ichneumoneus might have evolved to resemble.  Several individuals were encountered as they zigzagged urgently on dry sand deposits along the Mississippi River (where I had hoped, unsuccessfully, to find another locality for our intergrade population of Cicindela scutellaris).  Comparison of the individual in the photo with specimens in my collection (all identified by mutillid expert Kevin Williams, Utah State University) suggests this is Pseudomethoca simillima, and the photo is also a good match with other photographs of the species at BugGuide.  One thing that bothers me with the idea of this being a model for E. ichneumoneus is that I have not seen P. methoca commonly in Missouri (I have only three specimens in my collection), while E. ichneumoneus is one of our most common clerids.  There is another mutillid species in Missouri – Dasymutilla quadriquttata – that also seems to have potential as a model for E. ichneumoneus and that I have encountered much more commonly in the state.  However, D. quadriguttata is somewhat larger than E. ichneumoneus.  At any rate, other than the statement by Mawdsley (1994) that E. ichneumoneus seems to mimic mutillids, I can’t find that any more specific information has been recorded about the possible model(s) for that species.

As a caveat, I shall add that this mutillid was the… most… uncooperative… insect… that I have ever tried to photograph!  They really never stop moving, so you have to track the moving insect through the lens and fire shots when you think you’ve got it centered and focused.  Most of the time you don’t!  Using the Canon 1-5X macro lens for this did not make things any easier.  I tracked this female for quite a while and fired off a number of shots, only to get this one that I thought was fairly decent (and still just missed the focus on the near side of the pronotum).

Speaking of mutillids, I simply must photograph my specimen of Dasymutilla gloriosa (sometimes called the thistledown velvet ant) – you will not believe it!

Photo Details:
Pseudomethoca simillima: Canon MP-E 65 mm 1-5X macro lens on Canon 50D, ISO 100, 1/250 sec, f/14, MT-24EX flash 1/8 power w/ Sto-Fen diffusers. Minimal cropping and post-processing.
Enoclerus ichneumoneus: Canon 100mm macro lens on Canon 50D, ISO 100, 1/250 sec, f/14, MT-24EX flash 1/4 power w/ Sto-Fen diffusers. Minimal cropping and post-processing.

REFERENCE:

Mawdsley, J. R. 1994. Mimicry in Cleridae (Coleoptera).  The Coleopterists Bulletin 48(2):115-125.

Copyright © Ted C. MacRae

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Collection Inventory update

/ Ted C. MacRae / 3 Comments

The more observant – and taxonomically inclined – among my readers may have noticed the sidebar item entitled, “T. C. MacRae Collection”. The links within that item lead to Google documents detailing the species in those groups of insects that are represented within my collection. I am primarily a beetle guy, and within that vast taxon I focus mostly on the woodboring beetle groups Buprestidae and Cerambycidae and the tiger beetle family Cicindelidae. As you can see, however, I have inventories for several additional groups, including non-beetle families – a testament to my inability to suppress broad interest in insects as a whole. I don’t claim to be an expert in these other groups of insects, but I do enjoy learning about groups outside my chosen field of expertise. It’s a bit of a ‘throwback’ attitude – insect taxonomists of the 19th and early 20th centuries commonly studied multiple families or even orders of insects. This broad approach has largely disappeared in the past 50 years, as taxonomists increasingly have been forced to become narrowly focused on a single insect taxon. I can maintain this broad approach because, while I am a professional entomologist, I am a taxonomist only by avocation. My research is conducted at my own discretion and doesn’t rely on securing grants or fulfilling a departmental mission. Rather, it is directed only by what I find interesting and can reasonably afford in terms of time and expense.

The purpose of this update is twofold – to call attention to two recent additions to the list of inventories, and to explain how the inventories are constructed in the event that some future reader will want to utilize them for reference. In the past two weeks, I’ve received back material accumulated over the years in the families Mutillidae (velvet ants) and Asilidae (robber flies). This material had been sent to experts for identification – doctoral candidate Kevin Williams (Utah State University) graciously provided IDs for the velvet ants, while worldwide asilid expert Dr. Eric Fisher (California Department of Food and Agriculture) kindly identified the robber flies. For each of these groups, an inventory was constructed in which the species represented by my material are listed in the context of the group’s currently accepted higher classification. In each case, higher taxa not represented in my collection are indicated by lighter gray text. A similar approach has been used, to varying degrees, in the other listed inventories. The biggest one, Buprestoidea, represents the bulk of my collection, listing almost 1,500 species from around the world. In this case, not only is the complete higher classification indicated, but all currently recognized world genera are also listed, as well as all known North American species. Again, taxa not represented in my collection are indicated by lighter gray text. Similar inventories have been constructed for Cerambycidae and Cicindelidae, but in these cases the inclusion of taxa missing from my collection is limited to those occurring in North America – their combined worldwide fauna is simply too large for me to concern myself with, given my primary focus on the worldwide buprestoid fauna.

Regarding the Buprestoidea, Cerambycidae, and Cicindelidae – these are my chosen groups of interest in which I am actively building North American representation (worldwide for Buprestoidea). If anyone can provide specimens representing taxa not in my collection, please contact me directly. I am more than happy to exchange for such material. As for the other groups, they are primarily ‘just for fun’ – I collect them when convenient because they are interesting, but more importantly to make them available to others who might have a research interest in them. If anyone working in these groups sees species listed that are of interest to your research, please feel free to contact me for a loan or exchange. I have material in many additional groups not yet listed – inventories will be posted as they become available. If you have interest in a group not listed, please contact me and I’ll let you know what material I have available for loan/exchange.