Now you see me…

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…now you don’t!
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In a previous post, I lamented the fact that I had never actually seen a live antlion larva, or doodlebug (family Myrmeleontidae). Lovers of sand, I’ve seen their famous pitfall traps many times, especially in recent years as I’ve searched sand habitats for my beloved tiger beetles. Occasionally, I’ve stopped to jab my knife under a pit, give it a quick flip, and search the freshly turned sand for the maker of the pit – never seeing anything. It never bothered me much either – there were always beetles to catch!  Two weeks ago I returned to the sand prairies of southeastern Missouri to look for additional sites for Cicindela scutellaris (festive tiger beetle), and as we searched one particular site on the Sikeston Sand Ridge I once again saw the characteristic funnel-shaped pits amongst sparse vegetation in the sandy soil.  I decided this time I needed to give it a good effort – how can any self-respecting entomologist accept not having ever seen a live doodlebug?  As I’d done many times before, I kneeled down, gently put the tip of the knife about an inch away from the edge of the pit, and then jabbed its full length assertively into the sand and under the burrow and flipped it over.  Like previous times, I studied the turned sand and saw nothing.  I stirred the sand gently with the tip of the knife and studied it again – nothing.  I tried another burrow – again, nothing.  I decided right then and there that I was doing something wrong – I could not simply be picking ’empty’ pits.  I continued staring at the turned sand, and then I saw movement – I looked closer, and it seemed as though the sand itself was moving.  At last I made out its outline – I had finally succeeded in finding a doodlebug!  I dug up another burrow, and knowing what I was looking for this time I had no problem quickly locating the little creature.  I watched it as it lay motionless – perfectly camouflaged by its color and with sand grains sticking to its body, and chuckled as it buried itself almost instantly with a quick, backwards shuffle into the sand. Who knows how many doodlebugs I’d successfully dug up in the past, completely overlooking them as they lay disguised and motionless in the sand.

More than 100 species of antlions, representing at least 19 genera, live in the Nearctic Region, although much of this diversity occurs in the southwestern U.S. and Mexico.  Despite the commonly drawn association between antlions and pitfall traps, in North America only those in the genus Myrmeleon actually exhibit this behavior.  This larva dug a pit and so must represent a species of Myrmeleon – perhaps M. immaculatus, a common species in North America and one whose adult I observed last fall on a nearby sand prairie remnant.  Species in other genera have free-living larvae that hide under objects or roam underneath the sand, from where emerge briefly to hunt for prey.

For those interested in learning more about antlions, Mark Swanson has an excellent website called The Antlion Pit.

REFERENCE:

Swanson, M.  1996. The Antlion Pit: A Doodlebug Anthology. http://www.antlionpit.com/

Copyright © Ted C. MacRae 2009

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Body Invaders

In keeping with the parasitic theme I established in my last two posts, I happened upon this brief video promotion for a National Geographic special called In the Womb: Extreme Animals which will air this Sunday (May 10). The video features the offspring of a parasitic wasp (Cotesia glomerata) that has injected her eggs into a caterpillar — and now they’re ready to emerge! It’s a fascinating study of parasitoid-host relationships, filmed incredibly from inside the caterpillar! Watch the whole video for the wicked, surprising ending.

Viewing tips: after beginning play, click on “HQ” in the lower right corner to view the video in high quality. Or, click on the video itself to be taken to YouTube, where you have the option to watch the video in HQ and in full screen mode (2nd button from the lower right corner). You will be amazed!

Vodpod videos no longer available.

more about “Body Invaders“, posted with vodpod

Tip of the hat to Adrian, who posted this yesterday (but I really did find it on my own).

Copyright © Ted C. MacRae 2009

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Newly emerged rabbit bot fly

Cuterebra buccata_P1020896_2

First things first – congratulations to Mark Deering (Sophia Sachs Butterfly House, right here in St. Louis) and Rod Rood (Washington State University) for correctly identifying yesterday’s “What the heck?” as the cast puparium of an oestrid bot fly.  Mark eventually staked his claim on the genus Cuterebra, and Rod as well included this genus in his short list.  They are more astute naturalists than I – had I not found the newly emerged adult right next to it, I doubt that I would have known or figured out what it was.  Thanks also to the many other people who played the game – most were united in thinking it was some kind of insect, with many noting its distinctly abdominal appearance.  It seems, at least among my readers, that shed insect cuticle is a more popular quiz subject than plants.

Cuterebra buccata_P1020891_2I encountered this individual on open sandy ground while searching for my beloved  southeastern Missouri festive tiger beetles.  When I first saw the adult, it was on its back on the ground, feebly waving a couple of legs in the air.  I at first thought it was some kind of clumsy beetle but realized what it was as I approached it.  Clearly the fly was in distress, and I thought it odd that the puparium was laying on the ground next to it.  Bot flies in the genus Cuterebra have among the most deliciously gruesome of all insect life histories.  The ultra short-lived adults (lacking even functional mouthparts) lay their eggs near rodent and lagomorph burrow entrances, with the different species showing a fair degree of host specificity (Catts 1982).  When the fly larva hatches, it migrates to the host and enters the animal’s body through a natural orifice or break in the skin.  It then finds a subcutaneous location to feed, creating a cyst-like structure within a swelling of subcutaneous tissue and with a hole at the skin surface to allow respiration.  Once mature, the larva exits and drops from the host and burrows into the ground for pupation. We could find no emergence hole nearby, so perhaps the puparium was exposed by rain prior to emerging and suffered some desiccation, or perhaps the adult had gotten stuck in the tough puparium and pulled it to the surface as it emerged – burning its limited energy reserves in the process. At any rate, it is rather unusual to find these things emerging with the pupal case.

Cuterebra buccata_P1020894_2Cuterebra spp. are known collectively as New World skin bot flies (formerly family Cuterebridae, but now classified as a subfamily of Oestridae).  I suspected this was the rabbit bot fly (C. buccata) due to its general appearance – notably the red bands in the eyes, which is a characteristic of rabbit-infesting species.  However, the genus is diverse, with 34 recognized North American species – seven of which belong to the rabbit-infesting group (Sabrosky 1986).  I don’t have a copy of Sabrosky’s revision, and my efforts to locate it electronically turned up only retail listings for $70 or more.  That’s serious coin for someone who really needs to stay focused on his beetles, so I sent these photographs to bot fly specialist Jeff Boettner at the University of Massachusetts.  Jeff confirmed that it is indeed a Cuterebra rabbit bot and will confirm a species identity after checking his collection.

Jeff also sent the following note and interesting link:

Speaking of red eyed bots…there is one on Bugguide that a woman from NM posted. It is Cuterebra mirabilis and it may be the rarest photo on BugGuide. It’s only known from 2 previous specimens (also from NM). Its the largest of the rabbit bots. Much darker than yours.

Jeff notes that “mirabilis” in Latin means “extraordinary” – a truly appropriate name for this beautiful insect. Even though I am a devout coleopterist, I must confess – cuterebrids rock!

REFERENCES:

Catts, E. P.  1982.  Biology of New World bot flies: Cuterebridae.  Annual Review of Entomology 27:313-338.

Sabrosky, C. W. 1986. North American species of Cuterebra, the rabbit and rodent bot flies (Diptera: Cuterebridae). Entomological Society of America Thomas Say Foundation Monograph, College Park, Maryland, 240 pp.

Copyright © Ted C. MacRae 2009

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Wednesday “What the heck?”

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This might be the hardest nature quiz ever – I don’t think I would’ve ever figured out what this was had I not found what I did next to it.  I found it on my recent trip to look for Cicindela scutellaris (festive tiger beetle) in southeastern Missouri. Of course, now knowing what it is, the image does seem to provide enough clues about its identity – perhaps some crack naturalist will figure it out.

I’ll provide the answer with additional photos tomorrow.

Copyright © Ted C. MacRae 2009

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A festive (tiger beetle) birthday

Last Thursday was my birthday, and as has become my custom, I took the day off and went on my ‘Annual Season Opening Birthday Bug Collecting Trip.’  One or two of you might remember how these plans were scrubbed last year by a last minute business trip, during which I discovered Pipestone National Monument in southwest Minnesota. That experience – and the post that I wrote about it – remain high among my all-time favorites. Despite that, nothing was going to derail my plans to go collecting this year, and at 5:30 in the morning I awoke to begin what would turn out to be as enjoyable and successful a day as I could hope for. I had convinced my colleagues and long-time collecting buddies Rich Thoma and Chris Brown to take the day off as well and accompany me down to the lowlands of southeastern Missouri to search for additional localities of the festive tiger beetle – Cicindela scutellaris.

Records of Cicindela scutellaris in southeast Missouri

Records of Cicindela scutellaris in southeast Missouri

As far as is currently known – C. scutellaris is represented in Missouri by three highly disjuct populations in the extreme northwestern, northeastern, and southeastern corners of the state.  The two northern populations are unambigously assignable to the northern subspecies lecontei, although their absence from areas further south in Missouri along the Missouri and Mississippi Rivers remains a mystery.  The southeastern population apparently represents an intergrade population with influences from both lecontei and the southeastern subspecies unicolor.  While this population was discovered many years ago (I first collected it in the mid-1980s), it remained known only from sand forests in Holly Ridge Conservation Area on Crowley’s Ridge.  A second population was discovered several years ago on sand exposures in the extreme western lowlands near the Ozark Escarpment when Chris Brown and I began our formal survey of tiger beetles in Missouri, and last year I succeeded in locating several populations of the beetle in the critically imperiled sand prairie relicts located along the spine of the Sikeston Sand Ridge.

cicindela_scutellaris_p1020910_2This year, we wanted to determine if intergrade populations also occurred on the Malden Sand Ridge – the southernmost expanse of sand exposures in the southeastern lowlands.  We didn’t know if they did – presettlement sand prairies were less abundant on the Malden Ridge due to its higher soil organic content.  As a result, no sand prairie relicts survived the Malden Ridge’s complete conversion to agriculture.  Undeterred, I got onto Google Maps and scoured satellite imagery of the ridge and located several spots that seemed to have potential – even though they were agricultural fields, they appeared to be of sufficient expanse and with enough sand to possibly support populations of the beetle.

So, on the morning of April 23, my ‘Annual Birthday Season Opening Bug Collecting Trip’ began by meeting up with Rich and Chris and driving the 223 miles from Wildwood to Kennett to explore several locations for a beetle based only on the suggestion of a flickering computer screen.  The first of these locations was a bust – there was a house constructed right in the middle of the site that wasn’t on the Google Map.  cicindela_scutellaris_p1020889_2Maybe the beetle occurred here and maybe it didn’t, but the last thing I wanted to do on a Thursday morning was interrupt a homeowner from their morning routine and ask them if we could collect bugs in their front yard.  Besides, there was another locality just a couple miles up the road that looked equally promising.  We found the spot and drove by slowly – it was an agricultural field that looked like it had been fallow for at least a short time, and although it did not look great (not as much sand as I had hoped) we eventually decided that since we were there we might as well take a look.  It wasn’t long before we saw an individual near the highest part of the field, and through a couple hours of exploring and digging adult burrows we had observed a limited number of adults.  Success!  The landowner happened by while we were there and graciously allowed us to continue our searches.  Through her, we learned that the field had been under soybean cultivation during the previous season.  This was good news to learn that beetles were inhabiting sand exposures on the Malden Ridge despite its complete conversion to agriculture.

Having confirmed the occurrence of C. scutellaris on the Malden Ridge, we then began driving to the next putative locality some miles north along the ridge.  Along the way, Chris spotted a rather large sand expanse in another agricultural field right next to the highway.  cicindela_scutellaris_p1020906_2Even though I hadn’t detected it in my Google Map search, it looked promising enough to explore, and so we did a quick U-turn and found a place to pull over.  This spot can only be described as the ‘festive tiger beetle motherlode’ of southeast Missouri!  Even though the field was obviously under active agricultural use, the beetles were abundant within the fairly large expanse of exposed sand within the field (photo below).  We were quickly able to collect a sufficient series to document the beetle’s range of variation and set about obtaining additional photographs.  I felt fortunate to be able to photograph this mating pair, which nicely illustrates the white labrum of the male (top) versus the dark labrum of the female (bottom) – one character that distinguishes this intergrade population from the similar-appearing six-spotted tiger beetle (C. sexguttata – commonly encountered along woodland trails throughout the eastern U.S., and with both sexes exhibiting a white labrum).  Note also how the male is holding his legs out horizontally (a behavior I’ve seen with other mating pairs) and the more heavily padded tarsi on his front legs. The latter specialization is thought to aid in grasping and holding the female (Pearson et al. 2006), although in this instance it clearly is not serving that function, but I have not yet determined for what purpose the horizontal posturing of the front legs is all about (perhaps it is related to alarm behavior).

cicindela_scutellaris_habitat_p1020899_2We completed the day by documenting the occurrence of this species on the third of only three sizeable sand prairie relicts that remain on the Sikeston Sand Ridge – a private parcel located a few miles south of the other two preserves.  These observations have increased our confidence that C. scutellaris is secure in Missouri’s southeastern lowlands, and that – thankfully – no special conservation measures will be required at this time to assure its continued existence.  We also now have enough material on hand to characterize the range of variation exhibited by individuals across this population.  We hope this will allow a greater understanding of the relative influence of lecontei populations to the north versus unicolor populations to the south in contributing to the makeup of this population.

Since it was my birthday, it was appropriate that I should discover this “gift” next to the rim of my net after I slapped it over a mating pair of beetles.  I haven’t found a large number of Native American artifacts during my time in the field, but this has to be most impressive of those that I have found – it is in almost perfect condition, with only the smallest of chips off of one of the lower corners.  Edit 5/5/09: After a little research, I believe this to be a spear point from the Archaic period (12,000 to 2,500 years ago).

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p.s. – my 100th post!

REFERENCE:

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

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