Month: July 2012

Even a 12-year old can discover the larva of a rare, endemic species!

/ Ted C. MacRae / 13 Comments

Since discovering the larva of the rare, endemic Florida metallic tiger beetle (Tetracha floridana) in the small, intertidal mangrove marsh behind my sister-in-law’s condominium in Seminole, Florida three years ago, I’ve looked forward to subsequent visits to see the adults (they’re nocturnal) and gather additional material needed to write the larval description. I had to wait a few days on this year’s trip due to rain (it is Florida, after all), but eventually a dry evening came along and I began “suiting up” for my nighttime foray. Much to my delight, my 12-year old nephew Jack wanted to come with me. Jack had never been in the field with me before, but according to his mom he has become quite interested of late in science and biology. My daughter Maddie, also 12 years old (and a veteran of many trips to the field with me), also wanted to go, so together the three of us slathered on the insect repellent and headed into the dark towards the marsh.

Larva of Micronaspis floridana (Florida intertidal firefly) | Pinellas Co., Florida

We had only my headlamp as a light source, so the kids trailed behind me as I picked a line through the brush, across a small creek, and onto a ridge that snakes through the marsh that marked one of the areas where I had seen good numbers of the beetles last year. We collected a small number to keep alive and place in a terrarium of native soil, the hope being that they would lay eggs so I could obtain some 1st-instar larvae for the formal description, but what I was really looking for were larval burrows. As we (well, I) searched the ground in front of me with the lamp and the kids trailed behind me in the dark, Jack suddenly stopped and said, “What’s that?” I shone my light to where he was pointing but didn’t see anything and so resumed my search. Right away he said, “There it is again.” I asked if it was a rabbit (we’d seen them at the edge of the marsh during the day), and he said, “No, it’s like a light or something.” I turned off the lamp, and gradually the faint, green glow reappeared. I recognized the source of the light instantly as that of a larval firefly, although truthfully I have never actually seen an actual firefly larva. Seeing a great teaching moment for the kids, we walked to the light, knelt down, and shone the lamp directly on the ground from where the light was coming to find the small (~10 mm long) larva moving slowly through the moist, algae-covered rocks. It had the classic, retractable firefly head and curiously quadruply-spined tergites. I congratulated Jack on finding the larva, emphasizing that I would have never seen it myself had he not been there and been so observant despite not having a lamp.

Larvae of this species exhibit the retractable head characteristic of firefly larvae.

I went back a few nights later by myself so I could concentrate on photographing some of the things we saw in the marsh the previous night, including the firefly larva. I had no problem relocating one in the same place we found it before (I just turned off my headlamp and waited for the green glow). I’m generally not keen on posting photographs of unidentified insects (just me, but I find photos much more interesting when accompanied by the natural history back story), and I was sure this larva would remain unidentified (I have little knowledge of adult fireflies, much less their larvae). This seemed even more likely after perusing the few identified and many unidentified firefly larvae photographs on BugGuide and finding nothing even remotely similar. I was about to give up when I decided to try the search term “Lampyridae Florida Pinellas” (“Pinellas” being the county where we found the larvae—my thinking being that maybe there was a Florida firefly checklist that could narrow down to the county level the possible species), and high in the results was a page titled Florida intertidal firefly (fiddler crab firefly). On that page was a photo of the larva, although not nearly large and detailed enough to be sure it was the same, but still in my mind almost surely this species because of the stated restricted habitat—intertidal zone of Florida coastal salt marshes! I sent these photographs to lampyroid aficionado Joe Cicero, who kindly confirmed my identification. 

Restricted to intertidal marshes in coastal Florida.

Because it occurs only at the edges of salt water marshes around the peninsular coast of Florida, M. floridana is a classic example of shoestring geographic isolation and, thus, serves as a good model for studies of genetic isolation and its impact on speciation (Lloyd 2001). Along with T. floridana, it now makes at least two rare, Florida-endemics occurring in the small private, preserve behind my sister-in-law’s condominium (both of which were first found as larvae rather than adults). Although the larva of M. floridana is already known—albeit by a rough black and white photograph (McDermott 1954)—it’s rarity and restricted habitat nonetheless make it an exciting find well deserving of the more detailed color photographs shown here. However, as I told Jack after receiving confirmation of its identity, he gets full credit for the discovery. I took him into the field with me with the intention of showing him some new things, and he turned the tables on me! Yes, even a 12-year old can discover the larva of a rare, endemic species!

REFERENCES:

Lloyd, J. E. 2001. On research and entomological education V: a species concept for fireflyers, at the bench and in old fields, and back to the Wisconsian Glacier. Florida Entomologist 84(4):587–601.

McDermott, F. A. 1954. The larva of Micronaspis floridana Green. The Coleopterists Bulletin 8(3/4):59–62.

Copyright © Ted C. MacRae 2012

Planet’s Coolest Critters – Tiger Beetles

/ Ted C. MacRae / 4 Comments

Cicindela scutellaris rugifrons – photo by Harry Zirlin.

Readers of this blog know well (and hopefully share) my affection for tiger beetles (family Cicindelidae). That should come as no surprise, as tiger beetles rank among the most popular of all beetle groups. The reasons for this are many—for me it is their extreme polytopism (geographically based variation in coloration and markings), affinity for extreme habitats, and charismatic behavior (both adults and larvae), while for others it may be from a more basic research perspective (e.g., thermoregulatory behaviors, molecular phylogeny, and visual physiology) or as models for conservation research. I think most, however, will simply declare that tiger beetles are just… well, cool! That is the perspective of Harry Zirlin, who wrote this charming little article entitled, Planet’s Coolest Critters – Tiger Beetles at PetsLady. After introducing the group and its diversity, lifestyles, and behaviors, Harry notes the increasing popularity of tiger beetles with birders, butterfly watchers and nature photography buffs and the recent proliferation of field guides that have enabled their elevation to the ranks of “watchable wildlife.” Maintaining tiger beetles in terraria allows an even closer look at their beauty and behaviors, and Harry gives some useful tips on how best to accomplish this. It’s a pleasant little read, and I recommend you check it out!

Copyright © Ted C. MacRae 2012

Working with Cerceris fumipennis—Epilogue

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Cerceris fumipennis nest littered with Neochlamisus sp. beetles

In Working with Cerceris fumipennis Part 1 and Part 2, I talked about the use of this species as a biosurveillance tool for Buprestidae. These wasps are specialist predators of jewel beetles, which they capture almost exclusively and paralyze with their sting to use as food provisions for their offspring in underground nests. I also mentioned that there are other species of Cerceris, each specializing in its own distinct prey group, and at my site in east-central Missouri I found C. bicornis, a weevil specialist, almost as common as C. fumipennis. Thus, when I came upon this particular Cerceris wasp nest, I wondered it I had encountered yet another species in the genus, for littered around it were case-bearing leaf beetles in the genus Neochlamisus.

The bright coppery coloration suggests Neochlamisus platani

I counted 11 beetles lying on the diggings surrounding this nest, and as is typical with buprestids around C. fumipennis nests these beetles all appeared to represent the same species (I’ve done a little collecting of Neochlamisus beetles in Missouri—the especially bright coppery coloration suggests to me N. platani, a species found on eastern sycamore, Platanus occidentalis). I’ve also noted that C. fumipennis nests littered with beetles on the surface also have beetles—usually of the same species—freshly cached underground, so I decided to dig up the nest to see what might be in it. As I inserted the grass stem and started digging, I heard the distinctive buzzing indicating the wasp was still inside the nest, and when it appeared I noted the distinctive three yellow facial markings that identify it as a female C. fumipennis. As suspected, the nest contained another seven beetles of the same species, and I would later learn that C. fumipennis, while specializing on jewel beetles, does occasionally take other prey. Philip Careless and colleagues recorded two leaf beetles, including Neochlamisus bebbiana, and one weevil as hosts for this wasp at their Working with Cerceris fumipennis website. If my species ID of these beetles is confirmed, this should represent yet another non-buprestid host record for C. fumipennis, although I should also mention that out of several hundred observations this was the only non-buprestid prey I observed around or in a C. fumipennis nest.

Copyright © Ted C. MacRae 2012

Palmetto Tortoise Beetle, Hemisphaerota cyanea

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Hemisphaerota cyanea (palmetto tortoise beetle) on saw palmetto (Serenoa repens)| Levy Co., Florida

While most leaf beetles (family Chrysomelidae) are found associated with herbaceous plant species, many members of the subfamily Hispinae—which includes leaf mining beetles and tortoise beetles—are found on the foliage of woody plants. In North America the most distinctive of tortoise beetles found on trees is the palmetto tortoise beetle, Hemisphaerota cyanea. These distinctive dark blue, hemispherical-shaped (hence, the genus name) beetles with yellow antennae are found in the deep southeastern U.S. on the fronds of saw palmetto, Serenoa repens, and other native and introduced palms. I found the beetles in these photographs near Cedar Key Scrub State Preserve in Levy Co., Florida while searching white sand 2-tracks through sand scrub habitat for the Florida-endemic Cicindelidia scabrosa (Scabrous Tiger Beetle).

Beetles scarify the leaf epidermis, leaving trough-like feeding marks.

I first saw this species during my first insect collecting trip to Florida back in 1986. I didn’t know much then (other than that I really, really enjoyed traveling to different parts of the county to collect insects!). I was in Everglades National Park (with a permit) when I first noticed them dotting saw palmetto fronds. I think I had actually noticed them for some time but thought they were some type of scale insect before eventually realizing it was actually not only a beetle, but a tortoise beetle (one of the many groups of insects in which I was interested during those early, formative days).

Specially modified tarsi and a hemispherical shape allow the beetle to clamp itself tightly against the leaf to repel attack by ants and other insect predators.

I also remember being struck by how difficult it was to pry the adults off of the leaves on which they were sitting. It turns out that these leaf beetles have specially modified tarsi with thousands of bristles tipped with adhesive pads on the undersides. Normally only a few of the pads contact the leaf surface, but when the beetle is threatened it clamps all of them against the leaf and secretes an oil that strengthens the adhesive capabilities of the pads. Thus secured, the beetle clamps its hemispherical-shaped body down tightly against the leaf and is able to resist the efforts of ants and other predators to pry it from the leaf.

Copyright © Ted C. MacRae 2012

One-Shot Wednesday—Proctacanthus fulviventris ovipositing

/ Ted C. MacRae / 14 Comments

Proctacanthus fulviventris | Dixie Co., Florida

Today I spent the day just south of Florida’s “arm pit” to look for the state’s near-endemic tiger beetle Cicindelidia scabrosa (Scabrous Tiger Beetle). I first found this species last August on a white-sand 2-track through sand pine scrub habitat near Cedar Key Scrub State Preserve (Levy Co.). Although I was happy enough with the photographs that I got that day, the small spot of habitat that I found them in had yielded only a few specimens. My goal this time was to find the species in additional localities  to get a better idea of its precise habitat preferences and obtain a better series of specimens that more fully represents the range of variability exhibited by the species in its pubescence, color and elytral markings. By day’s end I would meet this goal, having found the species at four locations in Levy Co. and further north in Dixie Co. My first stop was actually in Dixie Co. near Lower Suwannee National Wildlife Refuge, where I found good numbers of individuals on a white-sand 2-track through pine scrub. A variety of robber flies (family Asilidae) were also seen along the 2-track, but I resisted the urge to photograph them because of the task at hand. Eventually, however, I came upon a female of this rather large species with her abdomen deeply inserted into the loose sand, surely in the act of oviposition. This was too much to pass up, so I set down the net, took off the backpack, and put the camera together. Unfortunately, in the time it took to do this, the fly had already withdrawn her abdomen and was rapidly “sweeping” the tip of the abdomen back and forth over the hole—I presume to cover and hide it. I snapped this first frame (the little bit of motion blur can be seen at the tip of the abdomen), but then I moved carelessly (not my usual habit) when scooting in for a closer shot. This spooked the fly and caused it to fly off, and I was left with this single image.

As much as I like robber flies, I can’t say that I’m well versed in their taxonomy. However, the large size (25–30 mm in length) and overall gestalt suggested to me that it belonged to the nominate subfamily, and cruising through online photographs eventually led me to Proctacanthus fulviventris. The individual seems to agree well with the description of this species provided by Hine (1911), including the bright yellow beard, black femora and red tibiae, and reddish abdominal terga. If my identification is correct, this species—like C. scabrosa—is also a Florida near-endemic whose distribution extends barely into southern Georgia. It’s dark coloration and light brown wings, combined with its large size, surely make it one of the more impressive-looking robber flies, and I’m sorry that I did not attempt to get more photographs of this species while I had the chance, as I did not see it at any of the other locations that I visited on the day.

Incidentally, by my interpretation the scientific name of this species translates to “yellow-bellied spiny-butt”!

REFERENCE:

Hine, J. S. 1911. Robberflies of the genera Promachus and Proctacanthus. Annals of the Entomological Society of America 4(2):153–172.

Copyright © Ted C. MacRae

Working with Cerceris fumipennis—Part 2

/ Ted C. MacRae / 19 Comments

During the 6-week period from late May to early July this year, I collected ~400 jewel beetle specimens representing at least 20 species (see Working with Cerceris fumipennis—Part 1). A final accounting of the species represented won’t be done until this winter, but the genera represented include Acmaeodera, Actenodes, Agrilus, Anthaxia (Haplanthaxia), Buprestis (Knulliobuprestis), Chrysobothris, Dicerca, Poecilonota, and Spectralia. Perhaps two-thirds of the specimens were “ground-picked”¹, while most of the remaining third were “stolen” directly from wasps by netting wasps in flight as they returned to their nest carrying prey.

¹ It’s not clear to me why I found so many abandoned buprestids at nest entrances. The wasps are known to drop prey when threatened and, rather than search for and relocate the prey, fly off to look for a new beetle(Careless et al. 2009). I observed this myself in several cases when I missed netting the wasp but swiped the net close enough to scare it, at which time it dropped the beetle and flew off (and I popped the beetle in a vial). However, the bulk of the beetles I found on the ground were not only at the nest entrance, but even mixed within the diggings surrounding the nest. My first act when checking each field was to check each nest, pick up any adults lying on top of the burrow diggings, and then carefully spread out the diggings with a knife or trowel to collect the beetles hidden within them. One nest contained as many as 13 Agrlus obsoletoguttatus inside the diggings. I wondered at one point if the wasps were leaving the beetles at the burrow entrance and then digging out the burrow before coming back to retrieve them, but I never actually witnessed this. On the other hand, I observed numerous wasps approaching their burrows while carrying prey, and every time the wasp dropped directly into the burrow. In fact, I could even predict what beetle species I was likely to find inside the nest based on the species I found around the entrance (more on that below).

This ball field with contains several dozen Cerceris fumipennis nests.

There is a third method that I used to collect beetles that I haven’t yet discussed, and that is digging them out of nests. In the latter part of the survey period (late June and early July), beetle numbers dropped rapidly, as did apparent wasp activity. As mentioned in the previous post, this drop off in activity came precisely at the time of season when I have observed buprestid beetle activity to decline in Missouri. As the drop off in activity was taking place, I began wondering what I would find if I tried digging up some of the burrows. Of course, digging up a nest takes much more effort than netting wasps or picking beetles up off of the ground, so it becomes important not only to identify whether a nest actually belongs to C. fumipennis and if it is active and likely to contain freshly captured beetles.  In addition, I observed the burrows of a variety of other insects in these fields as well, some of which are shown here and which might be confused with burrow entrances of C. fumipennis.

Cerceris fumipennis nest with Chrysobothris sp. adult left on diggings.

Cerceris fumipennis burrows exhibit perfectly circular, pencil-sized entrances surrounded by a symmetrical mound of diggings with a fine rather than granular texture. There are other Cerceris species that make nearly identical burrows, but they prey on other insects rather than buprestid beetles. At my site I found C. bicornis, a weevil specialist, almost as common as C. fumipennis. Their burrow entrances on the whole seemed slightly larger, but I could not use this as consistent distinguishing character. What I could use, however, was the presence of weevils rather than buprestids lying on the ground near the nest entrance. (I also observed this species returning to its nest and noted a rather faster, more powerful flight that made them even more difficult to capture than C. fumipennis). In contrast, there can be no doubt that the burrow above, with a buprestid beetle lying on the ground near the entrance, belongs to C. fumipennis.²

² The white plastic tag marks the burrow to facilitate locating nests on subsequent visits. It is secured with a golf tee and also can be rotated so that the hole covers the entrance. The hole is large enough to allow the wasp to leave but too small for a returning wasp to enter while carrying a beetle. The idea was to rotate the tags when I first entered a field to cover all the burrow entrances, watch for wasps returning with prey, and then net the wasps as they tried (in vain) to enter the burrow. However, I never actually observed a wasp trying to enter a covered burrow, even after leaving a field and returning 20–30 minutes later.

I presume this nest to be that of Bembix americana (sand wasp).

For the first few weeks, I thought the burrows such as that shown in the above photo also belonged to C. fumipennis. However, I never found beetles lying on the ground near the entrance, nor did I ever observe a wasp to enter or leave the burrow. I eventually noticed several distinct differences in burrow architecture—the burrow entered the ground at an angle rather than straight down, the diggings were distributed asymmetrically to one side of the entrance, and the latter seemed consistently a little larger than those of C. fumipennis. In addition, these burrows always seemed to be in the sandier portions of the fields. While I never associated any insect directly with these burrows, I did observe sand wasps (perhaps Bembix americana) in the vicinity and have seen similar-looking burrows dug by these wasps at Sand Prairie Conservation Area.

Larval burrows of Cicindelidia punctulata and other tiger beetles lack diggings around the entrance.

Tiger beetle larval burrows might also be confused with C. fumipennis burrows, especially after rain or high winds which can wash/blow away the diggings from around the entrance. I found adults of the punctured tiger beetle, Cicindelidia punctulata, fairly commonly at the site and presume the numerous tiger beetle larval burrows that were also present belong to that species. Larval tiger beetles burrows also enter the ground straight down and are, at first appearance, also perfectly round, but they are usually a little too small for C. fumipennis (those of Tetracha spp. being an exception)—the presumed C. punctulata burrow in the above photo measures about 5 mm in diameter. In addition, closer examination reveals a slight “D” shape to the burrow entrance (upper right in the above photo—the tiger beetle larva rests its jaws against the flat side) and, more distinctively, beveling of the ground around the rim of the burrow entrance. Cerceris fumipennis nests lack the slight D-shape and distinctive beveling.

Use a grass stem as a guide while carefully digging away the surrounding soil.

Years of practice digging up tiger beetle burrows prepared me well for my first attempts at digging up C. fumipennis burrows. While it might seem an easy task to follow a hole into the ground while digging soil away from it, in practice the burrow can be quickly lost after even a few inches due to falling soil covering the hole and making it impossible to relocate. I use a thin, flexible but sturdy grass stem to preserve the burrow path, inserting the stem into the burrow and down as far as it will go and then removing the soil carefully from around the hole with a knife or trowel. I try to avoid letting soil fall over the hole by prying the soil away from the hole, but if the hole does get covered the grass stem allows it to be easily relocated.

This nest contained a single Buprestis rufipes…

Cerceris fumipennis burrows are not very deep—only 10–15 cm, and angle to one side a few cm below the surface before leveling out near the bottom. I noticed the nest in the above photo because I saw a wasp fly into it. When I went over to look at it I found a Buprestis rufipes lying on the ground near the entrance and so decided to dig it up. As I expected, I found another B. rufipes at the bottom of the burrow (two above photos courtesy of Madison MacRae).

…while this one contained a cache of seven Agrilus quadriguttatus.

The above photo shows a cache of seven Agrilus quadriguttatus that I found at the bottom of another burrow. In this case, the prey is rather small compared to large prey such as Buprestis and Dicerca. While nests provisioned with species in these latter genera often contained only a single beetle in them, I nearly always found multiple beetles in nests provisioned with the smaller Agrilus species. One nest contained as many as 13 Agrilus obsoletoguttatus, among the smallest of the species I found utilized by C. fumipennis at this site.

Buprestidae taken from five different Cerceris fumipennis nests.

Some of the nests I dug up contained multiple species of beetles, but far more commonly I found only a single species in a given nest. The photo above shows the diversity and number of beetles found on one date after digging up five different nests. From top left the beetles are: 1) 1 Buprestis rufipes; 2) 2 Agrilus quadriguttatus and 1 A. obsoletoguttatus; 3) 2 A. quadriguttatus and 1 A. obsoletoguttatus; 4) 8 A. obsoletoguttatus; and 5) 2 Poecilonota cyanipes, 2 A. quadriguttatus, and 1 A. pseudofallax. It would make sense for wasps to provision nests with greater numbers of smaller beetles to ensure adequate food for their larvae to complete development. How the wasps actually locate their prey, and why this species has specialized almost exclusively on buprestid beetles, is a mystery (at least to me); however (and here comes the speculation du jour), I suspect the wasps may have keyed in on volatiles used by the beetles—either those released by suitable hosts or by each other to facilitate mate location. Use of buprestid pheromones or freshly dead host volatiles would allow wasps to more efficiently locate buprestid prey and, once locating a source (a tree harboring a particular beetle species), could return repeatedly to provision their nest fully. It seems less likely that wasps rely exclusively on visual location of prey, as this would involve a large amount of random searching through trees and passing up numerous, seemingly equally suitable prey.

REFERENCE:

Careless, P. D., S. A. Marshal, B. D. Gill, E. Appleton, R, Favrin & T. Kimoto. 2009. Cerceris fumipennis—a biosurveillance tool for emerald ash borer. Canadian Food Inspection Agency, 16 pp.

Copyright © Ted C. MacRae 2012

Working with Cerceris fumipennis—Part 1

/ Ted C. MacRae / 20 Comments

For nearly 30 years, jewel beetles (family Buprestidae) have been my primary research interest. While some species in this family have long been regarded as forest and landscape pests, my interest in the group has a more biosystematic focus. A faunal survey of Missouri was the result of my initial efforts (MacRae 1991), while later research has focused on distributions and larval host associations of North American species (Nelson & MacRae 1990; Nelson et al. 1996; MacRae & Nelson 2003; MacRae 2004, 2006) and descriptions of new species from both North America (Nelson & MacRae 1994, MacRae 2003b) and South America (MacRae 2003a). Research interest in other groups—especially longhorned beetles and tiger beetles, has come and gone over the past three decades; however, I always return to jewel beetles as  my first and favorite group.

In recent years, one species in particular—the emerald ash borer (EAB, Agrilus planipennis) has garnered a huge amount of research, regulatory, and public interest after reaching North America from Asia and spreading alarmingly through the hardwood forests of Michigan and surrounding states. The attention is justifiable, given the waves of dead native ash trees that have been left in its wake. With huge areas in eastern North America still potentially vulnerable to invasion by this species, the bulk of the attention has focused on preventing its spread from infested areas and monitoring areas outside of its known current distribution to detect invasion as early as possible. One incredibly useful tool that has been adopted by survey entomologists is the crabronid wasp, Cerceris fumipennis. Like other members of the family, these solitary wasps dig nests in the ground, which they then provision with captured insect prey. The wasp uses its sting to paralyzed the prey but not kill it, and once inside the burrow the wasp lays an egg on the prey and seals the cell with a plug of soil. The eggs hatch and larvae develop by consuming the paralyzed prey (unable to scream!). After pupation the adult digs its way out of the burrow (usually the next season), and the cycle begins anew. However, unlike other members of the family (at least in North America), C. fumipennis specializes almost exclusively on jewel beetles for prey. So efficient are these wasps at locating and capturing the beetles that entomologists have begun using them to sample areas around known wasp populations as a means of detecting the presence of EAB. Philip Careless and Stephen Marshall (University of Guelph, Ontario) and colleagues have been leading this charge and have even developed methods for transporting wasp colonies as a mobile survey tool and developed a sizeable network of citizen scientists throughout eastern North America to expand the scope of their survey efforts. Information about this can be found at the excellent website, Working with Cerceris fumipennis (please pardon my shameless lifting of the title for this post).

I first became aware of the potential of working with C. fumipennis a few years ago when Philip sent me a PDF of his recently published brochure on use of this wasp for EAB biosurveillance (Careless et al. 2009). My correspondence with him and other eastern entomologists involved in the work suggested that ball fields with lightly vegetated, sandy soil would be the best places to look for C. fumipennis nests, but my cursory attempts to find the wasp at that time were unsuccessful. I reasoned that the clay-soaked soils of Missouri didn’t offer enough sand for the wasps’ liking and didn’t think much more about it until last winter when I agreed to receive for ID a batch of 500+ buprestid specimens taken from C. fumipennis wasps in Louisiana. What a batch of material! In addition to nice series of several species that I had rarely or never seen (e.g. Poecilonota thureura), three new state records were represented amongst the material. A paper is now in progress based on these collections, and that experience catalyzed a more concerted effort on my part to locate a population of the wasp in Missouri. Museum specimens were no help—the only records from Missouri were from old specimens bearing generic locality labels such as “St. Louis” and “Columbia.” Throughout the month of May, I visited as many ball fields as I could, but the results were always the same—regularly groomed, heavy clay, barren soil with no evidence of wasp burrows (or any burrows for that matter).

Near the end of May, however, I had a stroke of luck. I had switched to a flatter route through the Missouri River Valley to ride my bike to work because of knee pain (now thankfully gone) when I saw this:

Practice fields at Chesterfield Valley Athletic Complex | St. Louis Co., Missouri

Those are “practice” fields in front of regular fields in the background, and unlike the latter, this row of nine fields (lined up against the levee adjacent to the Big Muddy National Wildlife Refuge) showed no evidence of regular grooming or heavy human use. Only ten miles from my home, I made immediate plans to inspect the site at the first opportunity that weekend. Within minutes after walking onto the lightly vegetated, sandy-clay soil of the first field, I found numerous burrows such as this:

Cerceris fumipennis with circular, pencil-wide burrow entrance and symmetrical mound of diggings.

Only a few more minutes passed before I found an occupied nest, the wasp sitting just about an inch below the entrance to its pencil-wide burrow. The three yellow markings on the face indicated it was a female (males have only two facial markings), and in short order I found numerous other burrows also occupied by female wasps. Some were just sitting below the burrow entrance, while others were actively digging and pushing soil out of the burrow with their abdomen. I flicked a little bit of soil into one of the burrows with a female sitting below the surface, which prompted an immediate “cleaning out” of the burrow—this explains the dirty face of the female in the following photo, but the three yellow facial markings are clearly visible:

Cerceris fumipennis female removing soil from burrow entrance.

After finding the burrows and their occupants, I began to notice a fair number of wasps in flight—leaving nests, returning to nests, and flying about as if searching for a ‘misplaced’ nest. A few of these were males, but most were females, and I also caught a couple pairs flying in copula (or at least hitched, if not actually copulating). Despite the number of wasps observed during this first visit, I didn’t see a single wasp carrying a buprestid beetle. This puzzled me, because all of the Louisiana beetles I had determined last winter were taken by standing in the midst of nests and netting those observed carrying beetles. Finally, I had confirmation that I was truly dealing with this species when I found a couple of beetles lying on the ground near the entrance to a burrow. These would be the only beetles that I would find on this visit, but subsequent visits during the following few weeks would show “ground picking” to be the most productive method of collecting beetles. Across the nine fields, I found a total of nearly 300 nests, and the wasps showed a clear preference for some fields over others—one field (P-6) had about 150 nests, while a few others had less than a dozen. The photo shown in ID Challenge #19 shows a sampling of ground-picked buprestids from P-6 in a single day, and occasionally I would find a real prize like Buprestis rufipes:

Buprestis rufipes laying near Cerceris fumipennis nest entrance.

Coincident with the appearance of large numbers of beetles laying on the ground near nest entrances, I also began to see wasps carrying their prey. Wasps carrying large beetles are easily recognized by their profile, but even those carrying small beetles look a little more “thick-thoraxed” (they hold their prey upside down and head forward under their thorax) and exhibit a slower, more straight-line flight path compared to the faster, more erratic and repetitively dipping flight of wasps not carrying prey. Learning how to discern wasps carrying prey in flight from the more numerous empty-handed wasps prevents a lot of wasted time and effort netting the latter. Nevertheless, there does appear to be some bias towards larger beetles when netting prey-carrying wasps in flight, as evidenced in the photo below of beetles taken by this method, also in field P-6, on the same date as the ground-picked beetles shown in ID Challenge #19. This could be a result of visual bias towards wasps carrying larger beetles, as in later visits (and presumably with a more refined search image) I did succeed in catching larger numbers wasps carrying smaller beetles (primarily in the genus Agrilus).

Buprestid prey of Cerceris fumipennis: L–R and top to bottom 2 Dicerca obscura, 2 D. lurida, 3 Poecilonota cyanipes, 2 Acetenodes acornis, 1 Chrysobothris sexsignata, 1 Agrilus quadriguttatus, and 1 A. obsoletoguttatus

All told, I collected several hundred beetles during my twice weekly visits to the site from late May to the end of June. Beetle abundance and wasp activity began to drop off precipitously in late June, which coincides precisely with the end of the adult activity period for a majority of buprestid beetles in Missouri, based on my observations over the years. This did not, however, spell the end of my activities in using C. fumipennis to collect buprestid beetles, which will be the subject of Part 2 in this series.

Congratulations to Joshua Basham, whose efforts in ID Challenge #19 earned him 12 points and the win. Morgan Jackson and Paul Kaufman were the only others to correctly identify the Cerceris fumipennis connection and take 2nd and 3rd, respectively. In an unexpected turn of events, BitB Challenge Session #6 overall leader Sam Heads did not participate and was leapfrogged by Brady Richards, whose becomes the new overall leader with 59 points. Sam now trails Brady by 5 points, while Mr. Phidippus lies another 3 points back. With margins this tight, the overall standing can still change in a single challenge, and there will be at least one more in this current session before an overall winner is named.

REFERENCES:

Careless, P. D., S. A. Marshal, B. D. Gill, E. Appleton, R, Favrin & T. Kimoto. 2009. Cerceris fumipennis—a biosurveillance tool for emerald ash borer. Canadian Food Inspection Agency, 16 pp.

MacRae, T. C. 1991. The Buprestidae (Coleoptera) of Missouri. Insecta Mundi 5(2):101–126.

MacRae, T. C. 2003a. Mastogenius guayllabambensis MacRae, a new species from Ecuador (Coleoptera: Buprestidae: Haplostethini). The Coleopterists Bulletin 57(2):149–153.

MacRae, T. C. 2003b. Agrilus (s. str.) betulanigrae MacRae (Coleoptera: Buprestidae: Agrilini), a new species from North America, with comments on subgeneric placement and a key to the otiosus species-group in North America. Zootaxa 380:1–9.

MacRae, T. C. 2004. Notes on host associations of Taphrocerus gracilis (Say) (Coleoptera: Buprestidae) and its life history in Missouri. The Coleopterists Bulletin 58(3):388–390.

MacRae, T. C. 2006. Distributional and biological notes on North American Buprestidae (Coleoptera), with comments on variation in Anthaxia (Haplanthaxia) viridicornis (Say) and A. (H.) viridfrons Gory. The Pan-Pacific Entomologist 82(2):166–199.

MacRae, T. C., & G. H. Nelson. 2003. Distributional and biological notes on Buprestidae (Coleoptera) in North and Central America and the West Indies, with validation of one species. The Coleopterists Bulletin 57(1):57–70.

Nelson, G. H., & T. C. MacRae. 1990. Additional notes on the biology and distribution of Buprestidae (Coleoptera) in North America, III. The Coleopterists Bulletin 44(3):349–354.

Nelson, G. H., & T. C. MacRae. 1994. Oaxacanthaxia nigroaenea Nelson and MacRae, a new species from Mexico (Coleoptera: Buprestidae). The Coleopterists Bulletin 48(2):149–152.

Nelson, G. H., R. L. Westcott & T. C. MacRae. 1996. Miscellaneous notes on Buprestidae and Schizopodidae occurring in the United States and Canada, including descriptions of previously unknown sexes of six Agrilus Curtis (Coleoptera). The Coleopterists Bulletin 50(2):183–191.

Copyright © Ted C. MacRae 2012

Cicada killer on the fly

/ Ted C. MacRae / 6 Comments

An eastern cicada killer (Sphecius speciosus) searches for her burrow | Jacksonville, Illinois.

I don’t normally spend much time trying to photograph insects in flight. To really do it right requires some rather specialized equipment, including very high-speed flash, and a bucketload of patience and skill. John Abbott exemplifies those whose great talent has produced stunning photographs of insects in mid-flight. That’s not to say that it can’t be done “on the fly,” so to speak, and even a hack like me can get lucky every now and then.

Earlier today I found a rather large number of eastern cicada killers (Sphecius speciosus) in a ball field in Jacksonville, Illinois. These impressive wasps are the largest wasp in eastern North America and have the rather gruesome habit of paralyzing cicadas with their sting, and then dragging them down into their burrows to be eaten alive by their grubs. I’ve recently become interested in solitary wasps (for reasons to be discussed later) and decided to see if I could get some decent photographs. I got a few I like (more on this later), but my favorite is this total luck-out shot of a wasp face-on in mid-flight. As I watched them, I noticed that each wasp spent a fair amount of time trying to identify its burrow amongst the dozen or more that were clustered along one side of the field. Occasionally they would land and search about a bit on foot, then take wing again to continue their search. I decided the best way to get a shot of one on the wing would be to watch for a wasp to arrive and begin its search. When I spotted one I would slowly close distance so I could be ready to get down on my elbows as soon as it landed (closing distance without spooking the wasp was not easy). I had just my center focal point set and autofocus turned on (normally I don’t use autofocus) and had already worked out a good flash exposure compensation setting. As soon as I got on my elbows, I would quickly frame the wasp and repeatedly trigger the autofocus as I got even closer, and when the wasp took flight I took the shot. This was still a crap shoot—I ended up with lots of out-of-focus and out-of-frame photos. Nevertheless, a few turned out fairly decent, one of which was this single, perfectly head-on and well-focused photo (though admittedly somewhat cropped).

Too bad I didn’t collect any of the wasps—at $49 each I could’ve made enough cash to buy that flash bracket I’ve been eyeing!

Copyright © Ted C. MacRae 2012