beetles

“Trying” to photograph whirligig beetles

/ Ted C. MacRae / 12 Comments

Nobody figured out exactly what I was doing in the photograph shown in the previous post (does anybody now see the whirligig beetles in the lower left corner of the photo?), but I sure enjoyed the guesses.  Several people alluded to dropping the camera or falling into the water, while others mentioned my heretofore unrevealed contortionist abilities.  However, Morgan Jackson‘s tale of trying to photograph Platypsyllus castoris has it all – rarely photographed species and the inordinate lengths we go through to get the shot.

Of course, whirligig beetles (family Gyrinidae) are much more commonly encountered than Platypsyllus castoris, but they can’t be any easier to photograph.  I spotted them as Rich and I balanced our way across a massive sycamore tree trunk while crossing the Black River during our early April hike of the lower Wappapello Section of the Ozark Trail.  I don’t know much more about whirligig beetles (or aquatic insects in general) than your average land-lubbin’ entomologist (in fact, I don’t think I’ve collected any since college systematics – yes, that long ago!), but for some reason I felt the need to try to photograph them.  Sure, the fallen tree provided a rare opportunity to get reasonably close to these very skittish insects without having to wade, but I think it was actually just the challenge of trying to photograph something in constant zigzagging motion that appealed to me.  Rich’s warnings that I would drop my camera were not enough to dissuade me, and after reaching the other side I ditched the backpack and tiptoed out with just my camera.

It seems like I’ve said this often in recent months, but these are my new hardest insect to photograph.  Not only are there the usual difficulties of framing and focusing a subject that is always in motion, but that motion is fast, erratic, and unpredictable, making tracking through the lens an extraordinary challenge.  Moreover, balancing precariously on a debris pile in the middle of the river strains the body and adds an element of danger (yes, I would be in deep doodoo if I dropped that camera).  I kept my eye on one particular individual that was swimming nearest to me, and after watching for a bit I saw that it was making a relatively predictable circuit that passed fairly close to me each time around.  I started trying to follow it through the lens and snap shots as it passed by – most of them turned out like this (actually, most of them turned out worse than this):

However, with each pass I got better, and I started getting shots with at least part of the beetle in focus.  So intent I was on what I was doing that I didn’t even know Rich had taken the photograph of me in the previous post until he showed it to me afterwards (he said he wanted to document the camera drop!).  Eventually I got this shot:

It’s far from a perfect photo – I had to adjust the levels because I hadn’t figured out the best lighting to use for something on the water’s surface, and the specular highlights from the flash on the forward elytron are rather extreme.  But the entire beetle is in focus, and we can make a reasonable guess as to its identity.  There are only two genera of whirligig beetles in Missouri – Dineutus and Gyrinus – and the large size (~12 mm in length) and hidden scutellum clearly identify this individual as something in the former genus.  Moreover, the rounded elytral apices (seen on other individuals as well) narrow it down even further to just a few possible species.  Unfortunately, they are distinguished primarily by ventral coloration; however, the bad first photo clearly does show dark legs, suggesting this may be D. ciliatus and not the orange-legged D. emarginatus.  I don’t even really care what species it is (did you ever think you’d hear me say that?), I’m just happy to have gotten a reasonably good photograph of an insect that surely few people have photographed well.

Copyright © Ted C. MacRae 2010

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Long Weekend Bug Collecting Trip!

/ Ted C. MacRae / 13 Comments

On Saturday, I’ll be joining a number of other Missouri biologists as a Group Leader for a BioBlitz at Penn-Sylvania Prairie (“C” on the map above).  Penn-Sylvania Prairie is a 160-acre tract of native tallgrass prairie in southwestern Missouri owned by the Missouri Prairie Foundation. I’ll be leading the “Beetles” group (of course), and as far as I can tell there has been little to no work done to survey beetles in this prairie.  Late May is an awesome time to look for beetles in southwestern Missouri, and with the forecast calling for sunny skies with highs in the mid-80’s, what better opportunity to add an extra day to an already long holiday weekend and do a…

Long Weekend Bug Collecting Trip!

The BioBlitz is not until Saturday afternoon, so I’ve padded the itinerary with a few nearby southwestern Missouri spots that I’ve wanted to visit for some time now.  The first stop will be Ha Ha Tonka State Park (“B”) and its mosaic of dolomite glades and post oak savanna.  My interest in this area stems from two jewel beetle specimens collected there by a student at the University of Missouri, who gave them to me for identification.  These two specimens caused a stir when I first saw them, as I could not definitely ID them – they resembled Agrilus impexus, a common inhabitant of the desert southwest and Mexico, but they were much larger and, of course, were found in Missouri.  These specimens played a key role in clearing up a case of taxonomic confusion on the identity of Agrilus impexus when I sent them to U.S. Agrilus-guru Henry Hespenheide.  Through comparison with type specimens, he determined that these were among a smattering of specimens collected across the Great Plains that represent the true A. impexus, while the common southwestern U.S. species to which the name had long been applied was actually an undescribed species.  He described the latter as Agrilus paraimpexus (Hespenheide 2007), and the true A. impexus remains rare and little known.  Obviously, my two specimens are the only ones known from Missouri, and indeed only one other specimen of this species has been collected in the past 60 years!  I know that makes finding it a long shot, but the student who collected them told me he swept them from woody vegetation along the edge of a glade at Ha Ha Tonka Savanna Natural Area.  I suspect they may be associated with honey locust (Gleditsia triacanthos), thus, I will have my beating sheet and will be beating lots of honey locust on Friday – wish me luck!

On Sunday, I’ll work my way slightly northeast to some of the sandstone glades that are found in St. Clair Co. where the Osage Plains to the west transition into the Ozark Highlands to the east.  The two most interesting of these are Lichen Glade Natural Area (“D”) and Dave Rock Natural Area (“E”).  Here, sandstone glades and bluffs are surrounded by dry and dry mesic sandstone woodlands dominated by post oak (Quercus stellata) and blackjack oak (Quercus marilandica).  Many years ago, I beat a single specimen of Agrilus frosti off of post oak at Lichen Glade.  I have not collected the species since, and I know of only one other Missouri specimen collected by state agriculture personnel in a malaise trap in central Missouri.  I also hope to photograph the lichen grasshopper (Trimerotropis saxatilis), which I have seen commonly at both of these sites.  This Great Plains species is at its eastern limit of distribution in Missouri, occurring exclusively on sandstone and igneous glades where its cryptic coloration makes it nearly invisible against the acidic, lichen-covered rocks that dominate these habitats.

Otherwise, I have no specific goals for the trip, but as late May is prime time in this area for jewel beetles, I’ll be doing lots of general beating on the oaks and hickories that many species in this family favor as hosts for larval development.

REFERENCE:

Hespenheide, H. A.  2007. The identity of Agrilus impexus Horn, a new species, and taxonomic notes and records for other Agrilus Curtis species (Coleoptera: Buprestidae).  Zootaxa 1617:57–66.

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Cylindera celeripes Larva Revealed

/ Ted C. MacRae / 22 Comments

In a recent post, I provided the first ever glimpse of the previously unknown larva of Cylindera celeripes, or swift tiger beetle.  This little-known flightless species is among the tiniest in North America (adults measure only 8 or 9 mm in length), and so far nobody has succeeded in rearing the species in the lab, or even finding its larva.  As the photographs in that post showed, I am reasonably close to accomplishing that first goal, having successfully obtained a number of eggs from field-collected adults placed in a terrarium of native soil. I fed the subsequent larvae a diet of small rootworm larvae and Lygus nymphs before putting them to sleep for the winter in a cold incubator, and the larvae resumed activity when I pulled them out of the incubator 2 months ago. Since then, they have feasted heavily on small noctuid larvae that we rear in our lab, and now most of the dozen or so larvae have sealed their burrows – I presume for pupation before (hopefully) emerging as adults in the next few weeks.

Cylindera celeripes 3rd instar larva - USA: Oklahoma, Woodward Co.

There is more to the story, however.  I had brought the adults back home in June 2009 from a population I found at Alabaster Caverns State Park in northwestern Oklahoma.  This was a reasonably robust population – news enough for a species that has not been seen in good numbers for many years now, and my discovery of equally healthy populations at several other locations in the general area gives new hope for the long-term prospects of a species that some regard as a potential candidate for listing as an endangered species. It also gave me hope that I might be able to find the larva were I to return to the area in the fall.  I also had a hunch that Cicindela pulchra (beautiful tiger beetle) could be found in the area, based on some very large larvae I found during that June trip, so in early October I made a quick return to northwestern Oklahoma to search for these two species.  While it was too cold and wet to have any hope of finding Cicindela pulchra adults (I still think the species is there), it did not prevent me from realizing my other goal.  May I present one of the first ever field-collected larvae of Cylindera celeripes!

Cylindera celeripes 3rd instar larva - closeup of hump on 5th abdominal segment with hooks to aid in securing the larva in its burrow

I found the larvae at Alabaster Caverns where I had found the adults earlier in June, and although the larval burrows were very small (only 2 to 3 mm in diameter), I knew what they were immediately when I saw them.  As I had observed for the adults, burrows tended to be near the edges of barren patches of soil in proximity to vegetation and not out in the middle of the barren areas.  This makes sense, considering where it would be more likely for prey to be encountered.  Because the weather was cold and gray, I didn’t see (or expect to see) larvae actively sitting at the tops of their burrows, so I began “fishing” to see if I could yank a few from their burrows.  I fished quite a few burrows for the first half hour or so, but none of my attempts were successful.  I began wondering if the larvae were even active at all or if they had already entered hibernation for the upcoming winter.  While I was fishing, I noticed that the burrows all seemed rather shallow – only about 6” or so (most tiger beetles, having larger larvae, dig burrows that are much deeper). This gave me an idea.  I went back to the truck and retrieved a small spade that I carry in case… well, I’d never actually used it before.  Anyway, I inserted a grass stem into a burrow and sunk the spade into the ground right next to it, making sure I got the spade at least as deep as the grass blade.  I then removed the spade and sunk it into the ground on the other side of the burrow, then pried until the entire chunk of soil came up intact.  With the bottom of the soil chunk exposed, I used my knife to carefully remove slivers of soil until I found the end of the grass stem that I had inserted into the burrow.  Carefully removing the soil in this area revealed the larva in a side chamber at the bottom of the burrow.  Success!  I took many photos of that larva right then and there, and over the next hour or so collected several more larvae, all but one of which I presumed were 3rd instars.  I packed each larva in its own small vial of native soil for the trip home, and although I have been attempting to rear them out for confirmation of their identity, there is little doubt that they do indeed represent this species.

Cylindera celeripes 3rd instar larva - that grotesquely beautiful head!

The photographs I’m showing here are not those first field photographs that I took when I first discovered the larvae.  Looking at those photographs after I returned home, I was dissatisfied with the amount of soil and debris that covered the larvae – especially their grotesquely unique head and pronotum.  Instead, I removed one of the larvae from its rearing tube and gave it a “bath” – brushing it with a fine camel-hair brush in a shallow dish of water – to clean it up for the photographs shown here.  After the photo shoot, I sacrificed this larva for the collection – it will be the basis for a formal description of the larva of this species (along with examples of the 1st and 2nd instars that I had sacrificed from my rearing, not yet confident that I would succeed in getting any of the others to 3rd instar).  The only thing I am waiting on before preparing that description is to see whether I actually succeed in rearing this species from egg to adult – stay tuned!

Photo Details: Canon 50D (ISO 100, 1/250 sec, f/13-16). Canon MP-E 65mm 1-5X macro lens, MT-24EX flash (1/8 power) w/ Sto-Fen diffusers. Typical post-processing (levels, unsharp mask).

Copyright © Ted C. MacRae 2010

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Introducing Chrysobothris caddo

/ Ted C. MacRae / 9 Comments

This set of photographs comes from my June 2009 trip to northwestern Oklahoma, which I found at Boiling Springs State Park in Woodward County. They represent only the second buprestid species that I attempted to photograph with my (then) new camera and macro lens setup, the first being Chrysobothris ignicollis which I found at nearby Four Canyon Preserve. The latter species is commonly associated with Juniperus throughout much of western North America – indeed, the individuals I photographed were found on freshly cut J. virginiana (eastern redcedar), and I have reared the beetle from dead branches of this and other Juniperus species. The individual in these photographs represents another species in the same genus – Chrysobothris caddo. It was also found on cut redcedar; however, it is not normally associated with that plant. In fact, it is not very well-known at all, as it was only just described in 2007 (and these may well be the first ever identified photographs of the species).

Chrysobothris caddo is one of a number of new species that were described by Wellso and Manley (2007) in their revision of the Chrysobothris femorata species-group from North America. I’ve previously mentioned the taxonomic difficulties associated with this group, last revised by Fisher (1942), and it had been known for some time that several species – including some unnamed – were masquerading under the “catch-all” taxon of Chrysobothris femorata. Normally, the only people who care about such situations are taxonomists and those who enjoy placing ID labels on specimens (me on both counts – I just hated those “Chrysobothris femorata species-group” labels).  However, there was farther reaching impact in this case since C. femorata is a widespread and important economic pest of shade and fruit trees (eggs are laid on the trunks of the trees, which are then damaged by the boring actions of the larvae that hatch from them). The Wellso/Manley revision has brought some degree of clarity to species limits within the group (doubling its number of described species), but they remain difficult to identify since their recognition relies upon “suites” of characters rather than single “key” characters. For example, we know this individual (a female, based on the form of the pygidium, or upper surface of the tip of the abdomen) represents C. caddo because (see if you can find the characters in the photos as we go here):

  • the antennae are narrowed to the apex (eliminating C. rugosiceps, which has the last antennal segment strongly quadrate)
  • the post-median (back of middle) foveae (circular impressions) of the elytra (wing covers) are joined (eliminating C. viridiceps, which has the foveae distinctly separated)
  • the pygidium is deeply impressed on each side of the middle (eliminating C. quadriimpressa, which has the pygidium shallowly impressed)
  • the pygidium lacks a hyaline (membranous) lateral margin (eliminating C. adelpha, which is unique in possessing this character)
  • the elytra have the posteriolateral margins arcuate and the tips bronze (eliminating C. femorata, in which the margins are straight and the tips reddish)
  • the elytral costae (longitudinal ridges) are connected by cross-veins and interrupted by the foveae (eliminating C. comanche, which lacks cross veins and has indistinct foveae)
  • the frons (face) has the callosities (elevated patches) transverse and bronze (eliminating C. shawnee, which has larger, bronze-black callosities)

Are you cross-eyed yet?! If not, there are four additional species in the group that are distinguished by similarly subtle character suites but whose geographical occurrence outside of Oklahoma (see checklist below) automatically eliminates them from consideration.

Chrysobothris caddo is primarily associated with Celtis (hackberry), and my finding it on redcedar is simply an incidental association. There was a large tree dump in the back area of the park with freshly cut wood from a variety of plant species – such tree dumps are famous collecting grounds for woodboring beetles in the families Buprestidae and Cerambycidae. However, little importance can be given to beetle-plant associations observed in such situations, with multiple potential host plant species in such close proximity to each other. The third photograph shows another female probing cracks in the bark of cut Ulmus rubra (slippery elm) with her ovipositor – perhaps she will have laid an egg or perhaps not, and if she did it is unknown whether the larva that hatched would be able to feed and develop successfully to adulthood on this non-preferred host.

For those with an interest in this group, following is a checklist of the species with their geographical distribution and preferred hosts:

  1. Chrysobothris adelpha Harold – eastern US and southern Canada west to Texas.  Primarily associated with Carya, also reared from Amelanchier and Prosopis.
  2. Chrysobothris caddo Wellso and Manley – Florida west to Arizona and north to Missouri, abundant in Texas.  Primarily associated with Celtis, reared also from Cercis and Ebanopsis [= Pithecellobium].
  3. Chrysobothris comanche Wellso and Manley – New Mexico, Texas, and Utah.  Associated exclusively with Juglans.
  4. Chrysobothris femorata (Olivier) – all continental states and Canada.  Associated with a wide variety of woody plant species, especially those in landscape and orchard settings.
  5. Chrysobothris mescalero Wellso and Manley – New Mexico and Texas.  Associated exclusively with Quercus.
  6. Chrysobothris quadriimpressa Gory and Laporte – eastern US west to Continental Divide.  Primarily associated with Quercus, reared also from Juglans, Liquidamber, and Sapindus.
  7. Chrysobothris rugosiceps Melsheimer – eastern US and southern Canada west to Texas.  Primarily associated with Quercus, reared also from Castanea.
  8. Chrysobothris seminole Wellso and Manley – Georgia and Florida.  Associated exclusively with root crowns of Chrysoma, making it the only species associated with a non-woody host.
  9. Chrysobothris shawnee Wellso and Manley – eastern US west to Colorado.  Primarily associated with Quercus, reared also from Salix and Prunus.
  10. Chrysobothris sloicola Manley and Wellso – Known only from Michigan in association with Prunus.
  11. Chrysobothris viridiceps Melsheimer – eastern US and southern Canada west to Continental Divide.  Associated primarily with Quercus, reared also from Carya, Prosopis, and Ulmus.
  12. Chrysobothris wintu Wellso and Manley – Arizona and California.  Primarily associated with Quercus, reared also from Salix and Prunus.

I have, over the years, collected numerous specimens of most of the species in this group (lacking only mescalero, seminole, and sloicola in my collection), with specimens now assignable to caddo, comanche, shawnee, and wintu included in the original type series as paratypes.

Photo Details: Canon 50D (ISO 100, 1/250 sec, f/14-16), Canon 100mm macro lens, Canon MT-24EX flash (1/4 ratio) w/ Sto-Fen diffusers. Typical post-processing (levels, unsharp mask, minimal cropping).

REFERENCES:

Fisher, W. S.  1942. A revision of North American species of buprestid beetles belonging to the tribe Chrysobothrini.  U. S. Department of Agriculture, Miscellaneous Publication 470, 275 pp.

Wellso, S. G. and G. V. Manley. 2007. A revision of the Chrysobothris femorata (Olivier, 1790) species group from North America, north of Mexico (Coleoptera: Buprestidae). Zootaxa 1652:1–26 (first page only).

Copyright © Ted C. MacRae 2010

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The Marvelously Cryptic Dicerca lurida

/ Ted C. MacRae / 7 Comments

Dicerca lurida on trunk of wind-thrown mockernut hickory (Carya alba).

This is Dicerca lurida (family Buprestidae), another of several woodboring beetle species that I found on the trunk of a large, wind-thrown mockernut hikcory (Carya alba) tree during my early April hike of the lower Wappapello Section of the Ozark Trail.  Actually, I had already spent some amount of time at the tree photographing a checkered beetle (Enoclerus ichneumoneus) and a longhorned beetle (Stenosphenus notatus) giving a ride to a phoretic pseudoscorpion before I even noticed not one, but several of these cryptically colored jewel beetles on the trunk of the tree.

Like other species in the genus, the brilliant metallic gaudiness of Dicerca lurida as a pinned insect specimen in a cabinet belies its near invisibility when sitting on the bark of its host trees.  Several different trees have been reported as hosts (Nelson 1975), but hickories of the genus Carya seem to be the most preferred.  The beetles rapidly colonize wind-thrown or cut trees and branches while the wood is still hard and strong, and I have collected it from a number of hickories and reared it from dead pignut hickory (Cary glabra) and shellbark hickory (Carya laciniosa), as well as sandbar willow (Salix exigua).  Most jewel beetles are active as adults only during a limited time during the season – typically late spring and early summer in eastern North America, but species of Dicerca occur as adults throughout the year – even during winter hibernating under loose bark.  This individual probably represents one of those hibernating adults that resumed activity in the first warm days of spring, searching for freshly killed host trees on which to mate and lay their eggs.  Widespread across eastern North America, it is perhaps the commonest species of the genus and one of the commonest jewel beetles in North America.  Yet, despite its abundance, year-round occurrence, relatively large size, and attractive coloration, its cryptic habits keep it seldom seen by those who don’t look for it.

Photo Details: Canon 50D (ISO 100, 1/250 sec, f/18), Canon 100mm macro lens, Canon MT-24EX flash (1/4 ratio) w/ Sto-Fen diffusers. Typical post-processing (levels, unsharp mask, minimal cropping).

REFERENCE:

Nelson, G. H. 1975. A revision of the genus Dicerca in North America (Coleoptera: Buprestidae). Entomologische Arbeiten aus dem Museum G. Frey 26:87–180.

Copyright © Ted C. MacRae 2010

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A Horridus Birthday

/ Ted C. MacRae / 36 Comments

For many years now, I’ve celebrated my birthday each year with the “season-opener-birthday-bug-collecting-trip.”  This happens regardless of what day of the week it falls (although two years ago I did get roped into a business trip – I made up for it by stumbling into a quick but thoroughly enjoyable tour of Pipestone National Monument before my flight back home).  Last year I made sure I got the day off and had a nice, festive (tiger beetle) birthday.  For this past April 23rd, a Friday, I celebrated my 29th birthday (for the 2-dozenth time!) by grabbing long-time field companion Rich and shooting down to Sam A. Baker State Park in the Ozark Highlands of southeastern Missouri.  My goal for the trip was to find the very uncommon Cladrastis kentukea (American yellowwood), a small tree that is known to occur in Missouri only in the White River Hills of the extreme southwest and in a few localities in and near Sam Baker State Park.  Actually, it wasn’t the tree so much that I was after, but a small jewel beetle – Agrilus cladrastis – that utilizes this plant exclusively for its larval host. To date, the only Missouri specimens of this species have been collected by the late, great Gayle Nelson on yellowwood in the White River Hills, and I wanted to see if I might be able to find it in southeastern Missouri as well.  April is still too early to encounter active adults, but my plan was to: 1) find examples of the tree, 2) collect dead wood from them, and 3) cut living branches to leave in situ for infestation this season and retrieval the next.  Long story short, I succeeded on all three counts (though I won’t know for a few weeks whether the wood I brought back actually harbors any as yet unemerged adults – finger crossed!).

The area where we expected to find the tree was steep, rocky slopes overlooking Big Creek on the north side of the park.  Rich and I were hiking a trail below the slopes, and I had gotten a little bit ahead of him when I saw a 30″ long snake stretched straight out across the trail.  Recognizing it immediately as one of our venomous species, but not quite sure which one, I blurted out, “Wow, what a gorgeous snake!”  Rich, a better herpetologist than I, shouted from a distance back, “What kind?”  In the few seconds during which this exchange was taking place, it all registered – the dark stripe behind the eye, the bold markings (too dark for a copperhead, too big for a western pygmy rattlesnake, too widely spaced for a massasauga), the black tail (not yellow-green like a juvenile copperhead), and a tiny little one-chambered rattle!  I yelled back, “A young timber rattler!”  Rich got there promptly, and we decided that it must be a yearling based on the time of year, its length, and the size of the rattle.

I have seen a few timber rattlesnakes (Crotalus horridus) in Missouri over the years, but never like this.  My previous sightings have all been fleeting glimpses after hearing them shooting into the underbrush to escape my close approach – me oblivious to their presence until it was too late.  This young snake, by contrast, didn’t flinch as I approached (carefully), set down the backpack, and assembled the camera to begin taking photographs.  As I began taking a few photos of the head area (from a respectful distance – the vision of that terrifyingly aggressive prairie rattlesnake from two years ago still lingers), it became agitated and started moving for cover.  Rich wasn’t too anxious to head it off at the pass, but I wasn’t satisfied with the shots that I’d gotten so far, so I grabbed my net to block it from disappearing into the litter.  That caused it to pause just long enough for me to get back into position and frame a shot… that I couldn’t get off before it started moving again!  We did this a few times until it finally just crawled right into the net – now what?!  I carried the net over to some large rocks on the side of the trail and used them to flip the net and dump out the snake, which immediately headed for cover underneath the rocks.  I figured the photo shoot was over then, but the space under the rocks was not deep, and after a bit of probing for escape routes the snake eventually settled into a money pose and I was able to snap away with glee – what do you think?

Missouri has five venomous snake species, all of which are pit vipers with three being rattlesnakes.  I’ve featured two of these in previous posts – the Osage copperhead and the western pygmy rattlesnake.  Both of these species occur throughout the Ozark Highlands, although the latter is more common in the southwestern part of the state.  The third rattlesnake species in Missouri, eastern massasauga, is rare in wet habitats scattered across northern Missouri, while the cottonmouth (or water moccasin) is limited to stream, river, and swamp habitats in the southern Ozarks and southeastern lowlands.  Many internet references list the western massasauga also as occurring in Missouri, but this subspecies is not included in the most recent Snakes of Missouri (Biggler and Johnson 2004).  Within Missouri, timber rattlesnakes have a statewide distribution, but they have been extirpated by humans from many areas and now occur as small populations in scattered locations across the state.  The same is true in other parts of their range as well, particularly along the western and northern limits.  It is thus a rare and exciting treat to see one of these magnificent animals, although the reasons for its rarity are both sobering and maddening.

REFERENCE:

Briggler, J. and T. R. Johnson.  2004. Snakes of Missouri. Missouri Department of Conservation, Jefferson City, 16 pp.

Copyright © Ted C. MacRae 2010

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Hitchin’ A Ride

/ Ted C. MacRae / 17 Comments

One of the more common species of longhorned beetles (family Cerambycidae) in Missouri, and throughout the eastern U.S., is Stenosphenus notatus.  Despite its commonness, however, it is a species that is easily overlooked because of its very early seasonality, emerging during the first warm days of spring (late March here in Missouri) and disappearing by the time the bulk of longhorned beetle species become active during late spring and early summer.  I found this individual on a recently fallen mockernut hickory (Carya alba) during the 2nd week of April, as Rich and I hiked the lower portion of the Wappapello Section of the Ozark Trail in southern Missouri (along with several other wood boring beetles species such as Dicerca lurida, Megacyllene caryae, and the woodboring beetle predator Enoclerus ichneumoneus).  Longhorned beetles display a variety of host fidelities, ranging from highly polyphagous to strictly monophagous – this species falls near though not quite at the latter end of the spectrum, being associated almost exclusively with the genus Carya (hickories and pecan).  I have reared adults from dead branches and trunk sections of not only C. alba, but also C. aquatica (water hickory), C. laciniosa (shellbark hickory), and C. ovata (shagbark hickory) (MacRae 1994, MacRae and Rice 2007).  Linsley (1963) also records Celtis (hackberry) as a host, but I have not seen the species myself in association with plants of that genus, nor have I seen other literature references to such – I suspect this may, in fact, be an incidental adult association rather than indicative of a true larval host (an all too common problem in interpreting literature on woodboring beetle host plants).

The very early spring occurrence of this insect can be traced to a peculiarity of its life cycle shared by few other cerambycid species in the eastern U.S. – overwintering in the adult stage.  Most eastern U.S. longhorned beetles overwinter within the host wood as either partially or completely grown larvae.  Warming temperatures in the spring trigger resumption of growth in the former and a transformation to the pupal stage in the latter, which emerge as adults a few weeks later during mid-late spring.  In contrast, S. notatus – which requires two seasons to complete its development – pupates in the latter part of the second season and transforms into the adult before the onset of winter.  When warm temperatures return in spring, the adults are ready to emerge and search out fresh hickory wood that has died within the past few months on which to lay their eggs and begin the cycle anew.

As I photographed this individual, I noticed an object attached to its left mesothoracic (middle) leg.  Zooming in on the object showed it to be a pseudoscorpion – a type of arachnid (relative of spiders, mites, and true scorpions) in the order Pseudoscorpiones.  I have not the resources nor the expertise to attempt a more specific ID, but its attachment to the beetle almost surely represents an example of phoresy – defined as a phenomenon in which “one animal seeks out and attaches to the outer surface of another animal for a limited time during which the attached animal (termed the phoretic) ceases feeding and ontogenesis, such attachment presumably resulting in dispersal from areas unsuitable for further development, either of the individual or its progeny” (Farish and Axtell 1971).  Pseudoscorpions have been reported attached to insects from several orders, primarily Diptera but also beetles and including longhorned beetles (Perry et al. 1974, Haack and Wilkinson 1987).  Many species of pseudoscorpions develop beneath the bark of dead trees and prey upon the many other small insects and mites found there, and it would be reasonable to presume that their most effective means of dispersal to new habitats (i.e., dead trees) would be by “hitching a ride” with adult woodboring beetles as they emerge and fly to these new sites.  As obvious as this explanation might seem, few data have actually been generated to demonstrate it is actually the case, and several competing hypotheses such as accidental boarding (hitching a ride by accident), obligate symbiosis (the pseudoscorpions live exclusively on the beetles), and phagophily (preying upon other beetle associates such as mites) have been offered as alternative explanations. However, at least one fairly recent investigation on the pseudoscorpion, Cordylochernes scorpioides, a frequent inhabitant under the elytra of the giant harlequin beetle, Acrocinus longimanus (family Cerambycidae), does seem to not only support the dispersal hypothesis, but also suggests that large male C. scorpioides even defend a beetle’s abdomen as a strategic site for intercepting and inseminating dispersing females (Zeh and Zeh 1992).

REFERENCES:

Farish, D. J. and R. C. Axtell. 1971. Phoresy redefined and examined in Macrocheles muscaedomesticae (Acarina: Macrochelidae). Acarologia 13:16–29.

Haack, R. A. and R. C. Wilkinson. 1987. Phoresy by Dendrochernes Pseudoscorpions on Cerambycidae (Coleoptera) and Aulacidae (Hymenoptera) in Florida. American Midland Naturalist 117(2):369–373.

Linsley, E. G. 1963. The Cerambycidae of North America. Part IV. Taxonomy and classification of the subfamily Cerambycinae, tribes Elaphidionini through Rhinotragini. University of California Publicatons in Entomology 21:1–165, 52 figs.

MacRae, T. C. 1994. Annotated checklist of the longhorned beetles (Coleoptera: Cerambycidae and Disteniidae) known to occur in Missouri. Insecta Mundi 7(4) (1993):223–252.

MacRae, T. C. and M. E. Rice. 2007. Distributional and biological observations on North American Cerambycidae (Coleoptera). The Coleopterists Bulletin 61(2):227–263.

Perry, R. H., R. W. Surdick and D. M. Anderson. 1974. Observations on the biology, ecology, behavior, and larvae of Dryobius sexnotatus Linsley (Coleoptera: Cerambycidae). The Coleopterists Bulletin 28(4):169–176.

Zeh, D. W. and J. A. Zeh. 1992. On the function of harlequin beetle-riding in the pseudoscorpion, Cordylochernes scorpiones (Pseudoscorpionida: Chernetidae). Journal of Arachnology 20: 47––51.

Copyright © Ted C. MacRae 2010

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Friday Flower – Pawpaw

/ Ted C. MacRae / 28 Comments

As my friend Rich and I stood in the verdent understory admiring the spectacular panicles of red buckeye punctuating the green lushness, a small brown flower on a leafless branch above me caught my eye.  “Pawpaw!” I exclaimed, perhaps partly in amazement that it took us awhile to notice the trees that were, in fact, all around us.  Pawpaw (Asimina triloba) is a member of the only temperate genus in the otherwise exclusively tropical and subtropical family Annonaceae (Custard Apple Family).  Although not nearly as restricted in occurrence in Missouri as the red buckeyes with which they were growing, they are nevertheless always a treat to see. Scattered throughout the state, they can be found growing in bottomland forests, ravines in mesic upland forests, along woodland streams, and at bases of bluffs (Yatskievych 2006).

Pawpaws are, of course, famous for their large edible fruits, sometimes called Indian bananas, Missouri bananas, Michigan bananas, [insert eastern state here] bananas, etc.  Technically, however, the pawpaw fruit is a berry, since it is derived from a single pistil and has multiple seeds embedded within the pulpy matrix.  I’ve not tried the fruit myself, not for lack of desire but rather an inability to find them when they ripen in fall before the birds and mammals get to them.  Some effort has been made to cultivate the plant for fruit production, but low fruit set seems to be a persistent problem due to reproductive self-incompatibility.

Pawpaw also famously serves as the larval food plant for the zebra swallowtail butterfly, Eurytides marcellus (family Papilionidae).  Beyond this, however, there seem to be not many insects associated with the plant.  I have collected dead wood of pawpaw in an effort to determine the species of wood-boring beetle species that are associated with it.  The only species I’ve reared is the longhorned beetle, Elaphidion mucronatum (whose common name “spined oak borer” belies the fact that it is one of the most polyphagous of all North American species), and two other longhorned beetles, Eupogonius pauper and Urgleptes querci (also highly polyphagous), have also been reported being reared from dead wood of this plant.  I have not associated any jewel beetles with pawpaw, nor have any such associations been reported in the literature.  It would appear that woodboring beetles are not fond of the soft, weak wood of pawpaw, perhaps due to the plant’s annonaceous acetogenins with known pesticidal qualities (Ratnayake et al. 1993) (acetogenins are also under investigation as anti-cancer drugs).  Other poisonous compounds, chiefly alkaloids, are found in various parts of the plant, especially the seeds and bark, and likely play a role in herbivore defense. Insect pollinators also seem to be infrequent, as I have not noted any insects on its flowers. Most members of the family are pollinated by beetles (Yatskievych 2006), but the meat-colored, downward-facing, not-so-sweet-smelling flowers of pawpaw suggest pollination by flies, perhaps those attracted to carrion.

REFERENCE:

Ratnayake, S., J.K. Rupprecht, W.M. Potter, and J.L. McLaughlin. 1993. Evaluation of the pawpaw tree, Asimina triloba (Annonaceae), as a commercial source of the pesticidal annonaceous acetogenins. p. 644-648. In: J. Janick and J.E. Simon (eds.), New Crops. Wiley, New York.

Yatskievych, G. 2006. Steyermark’s Flora of Missouri, Volume 2. The Missouri Botanical Garden Press, St. Louis, 1181 pp.

Copyright © Ted C. MacRae 2010

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