Phocus on Phyllobrotica

Beetles are often pretty good botanists, and when it comes beetle botanists there are none finer than species in the family Chrysomelidae. Members of this family are commonly called “leaf beetles” because… well, they are usually found on leaves, and with nearly 40,000 known species (and probably many more still unknown) it is one of the largest animal families on the planet! In fact, LeConte & Horn (1883)—the fathers of coleopterology in the United States—surmised that the function of leaf beetles “is to hold the vegetable world in check by destroying … the leaves”!

Here in Missouri we have 351 species and subspecies of leaf beetles (Riley & Enns 1979, 1982), the vast majority of which specialize on a limited range of host plants. Most restrict themselves to feeding on plants within the same family, and some to just a single plant genus or even species! Such specialization does not necessarily make a species rare—western corn rootworm (Diabrotica virgifera) develops almost exclusively on corn (Zea mays), yet it is one of the most abundant leaf beetles in the state, and among non-pest species the dogbane leaf beetle feeds almost exclusively on common dogbane (Apocynum cannabinum) yet is one of our most commonly encountered leaf beetles. There are, however, many other species of leaf beetles in the state that are rarely seen. Almost always they are also extreme host specialists, and there is no better example of this than species in the genus Phyllobrotica.

Eighteen species and one subspecies of Phyllobrotica are known to occur in North America (Riley et al. 2005, Gilbert 2009), of which five have been recorded in Missouri (Riley 1979, Riley & Enns 1979). With one glaring exception (see below), all of the species for which host plants are known restrict their feeding to one of two closely related genera in the mint family (Lamiaceae)—Stachys for most of the western U.S. species, and Scutellaria for most of the non-western U.S. species (Farrell & Mitter 1990). Of the five species in Missouri, only P. limbata has been encountered with any regularity; Riley & Enns (1979) recorded 61 specimens from six widely scattered counties in Missouri, many of them observed on S. ovata or S. lateriflora. A second Missouri species, P. physostegiae, now also is encountered reliably in southwestern Missouri; however, it wasn’t even described until 1979 due to earlier confusion with the enigmatic P. antennata (apparently still known only from the type collected in Tennessee) (Riley 1979). Prior to this, only a handful of specimens were known, three of which had been more recently collected by Rev James Sullivan of St. Louis on plants in the genus Physostegia (also in the mint family). Followup collections turned up large series of beetles on this plant at several locations in southwestern Missouri, and the species was formally described (Riley 1979). Farrell & Mitter (1990) suggest the unusual host is an example of isolated host transfer due to the unusual natural history of P. physostegiae, which along with its sister species is unique in the genus in that it inhabits dry prairie habitats rather than wet bottomlands. Species of Scutellaria inhabiting dry prairies are often annual and more unpredictably available than those inhabiting more mesic habitats, which could have favored broadened host range or shift by the ancestral P. physostegiae population to a related, chemically similar perennial host such as Physostegia (insects typically use volatile plant chemicals, in addition to vision, as informational cues for recognizing their host plants—Visser 1986).

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Phyllobrotica lengi Linell

The three remaining species of Phyllobrotica in Missouri—P. circumdata, P. lengi, and P. nigritarsis—all continue to be among the rarest beetles in the state. The first was never even collected in Missouri until Rev. Sullivan collected 8 specimens—all on S. incana—in a few eastern counties in Missouri in the late 1970s (recorded as “P. discoidea” in Riley & Enns 1979). As far as I can tell, no online images of this species exist, despite it being the most widely distributed species of the genus in North America (Farrell & Mitter 1990, Riley et al. 2003). The second species, P. lengi, was known from Missouri by just four specimens collected in the late 1800s (Riley & Enns 1979) until Rev. Sullivan collected a small series on S. parvula in east-central Missouri in 1988. Like P. circumdata, apparently no online image of this species exists as well—until now… the image above taken of one of the specimens in that small series, which Rev. Sullivan graciously gifted to me shortly after collecting them. The third species, P. nigritarsis, likewise was also known from Missouri by only four specimens—also collected in the late 1800s (Riley & Enns 1979)—until Rev. Sullivan collected a small series in association with S. parvula in east-central Missouri in 1987. Unlike the previous species, however, a single online image does already exist for this species at BugGuide, and the image below—again taken from a specimen in the small series kindly gifted to me by Rev. Sullivan—adds a second.

[Incidentally, both of these photos were taken for a new book by Rev. Sullivan that has just been published—more on that soon!]

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Phyllobrotica nigritarsis Blatchley

Are there additional species of Phyllobrotica in Missouri? Possibly! Phyllobrotica decorata has a known distribution almost as broad as P. circumdata, including several states surrounding Missouri (Illinois, Iowa, and Kansas), and two other eastern U.S. species—P. stenidea and P. vittata—have been collected as far west as Indiana (Riley et al. 2003). There is also the enigmatic P. antennata from Tennessee. Targeting plants in the genus Scutellaria wherever they may be found growing will likely turn up these species, if they occur here, or at least provide additional records for the other species already known from Missouri.

REFERENCES:

Farrell B. D. & C. Mitter. 1990. Phylogenesis of insect-plant interactions: Have Phyllobrotica leaf beetles (Chrysomelidae) and the Lamiales diversified in parallel? Evolution 44(6):1389–1403 [preview].

Gilbert , A. J. 2009. A new species of Phyllobrotica Chevrolat, 1836 (Coleoptera: Chrysomelidae) from California, USA, with notes on the western United States species. The Pan-Pacific Entomologist 84(4) [2008]:269–279 [abstract].

LeConte, J. L. & G. H. Horn. 1883. Classification of the Coleoptera of North America. Smithsonian Miscellaneous Collections 26(507):1–567.

Riley, E. G. 1979. A new species of Phyllobrotica Chevrolat (Coleoptera: Chrysomelidae) from the prairies of southwestern Missouri. The Coleopterists Bulletin 33(3):331–335.

Riley, E. G., S. M. Clark & T. N. Seeno. 2003. Catalogue of Leaf beetles of America North of Mexico. The Coleopterists Society Special Publication No. 1, 290 pp.

Riley, E. G. & W. R. Enns. 1979. An annotated checklist of Missouri leaf beetles (Coleoptera: Chrysomelidae). Transactions of the Missouri Academy of Science 13:53–83.

Riley, E. G. & W. R. Enns. 1982. Supplement to an annotated checklist of Missouri leaf beetles (Coleoptera: Chrysomelidae): new state records and host plant associations. Entomological News 93(1):32–36 [full text].

Visser, J. H. 1986. Host odor perception in phytophagous insects. Annual Review of Entomology 31:121–144 [pdf].

© Ted C. MacRae 2019

Posted in Chrysomelidae, Coleoptera | Tagged , , , | 4 Comments

‘Beetles in the Bush’ has it’s own domain!

I have a new post almost ready (about tiny little botanists!), but I wanted to let everybody know that this site—’Beetles in the Bush’—now has it’s own domain:

http://beetlesinthebush.com

No need to add “.wordpress” anymore. Update your links (but old links should still work).

© Ted C. MacRae 2019

Posted in [No taxon] | Tagged , | 1 Comment

Orchid Valley Natural Area

This month’s destination for the WGNSS Natural History Photography Group was Orchid Valley Natural Area in Hawn State Park. This natural area is south of the main park and not normally open to the public, but we were granted permission to enter by the park administration. Our targets were several species of orchids and other rare plants that are known to occur in the area—showy orchis (Galearis spectabilis) being the one I hoped most to see.

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Our group for the day (front to back): me, Lynne, David, Casey, Avery, James, Bill, and Rich (Chris behind tree at back).

There are no trails here—not even a place to park, as we squeezed our cars against the side of the road at a spot that appeared to provide good access. A bit of GPS-guided bushwhacking brought us to increasingly rough and sloping ground that ended up at the edge of a cliff overlooking one of the sandstone box canyons that this area is know for—down below was where we wanted to go. Wild azaleas lined the upper canyon edges with their stunning pink blossoms. We followed the canyon edge and found a way down, then circled back into the canyon to find a stunning waterfall, its sandstone walls dripping with mosses and ferns. We spent quite a bit of time here photographing the waterfall and surrounding area before eventually resuming the search for the orchids that we came to see.

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Bill surveys a waterfall at the center of a sandstone box canyon.

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The waterfall fell about 25 feet onto the sandstone rocks below, its splash creating perfect conditions for luxurious growth of mosses and ferns.

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Mosses sending up their “stems” (actually setae), each holding up a capsule filled with spores.

Sadly, the orchids were not yet in bloom—not even close, another victim of the cold, late spring we’ve been experiencing. Casey, our group leader, did find some very small showy orchis leaves, and we saw some nice clumps of another native orchid, rattlesnake plantain (Goodyera pubescens), an evergreen orchid that blooms during late summer. We hiked up another drainage that led to another box canyon—lacking a waterfall but equally impressive, nonetheless—but found no orchids in bloom there, either. We did, however, see cinnamon ferns sending up their spike-like fertile fronds and aggregations of antlion larvae (a.k.a. “doodlebugs”) in the soil beneath the sandstone ledges.

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Leaves of rattlesnake plantain (Goodyera pubescens).

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Moss growth is luxuriant in the wet sandstone exposures inside the box canyons.

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Sandstone ledge above a box canyon.

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Pits of antlions, or “doodlebugs”, clustered in the soil beneath a sandstone ledge. Ants and other insects that fall into the pits are quickly dispatched by the sickle-shaped mandibles of the bug lying buried at the bottom of the pit.

You might think failure to find what we were looking for would result in a disappointing field trip—far from it! Time in the field with like-minded friends in a beautiful spot is always a pleasure, and when it comes to searching for rare plants (or insects, or whatever), failure is the norm—making success, when it does come, that much sweeter. There will be other chances to see showy orchis (perhaps in a couple of weeks).

© Ted C. MacRae 2019

Posted in Myrmeleontidae, Neuroptera, Orchidaceae | Tagged , , , , , , , , , , | Leave a comment

“62nd” Annual “Season-Opener-Birthday-Bug-Collecting-Trip”

This past Tuesday was my birthday, and as I have done for my entire adult life I took the day off and went on my traditional “Season-Opener-Bug-Collecting-Trip”. In the past I’ve usually just had one friend go with me, but today I had three—Rich, Chris, and Bill!

We started off by heading south about 3½ hours to Tingler Prairie Natural Area in Howell Co.. I wanted to come here because: 1) it was a place I’d never visited before, and 2) there is a population here of the endemic Ozark trillium (Trillium viridescens) that I thought might be in bloom. Rain in the forecast and a patch of the real thing on the way down had us a little worried, but the day turned out spectacular with temps climbing to 80°F and skies partly to mostly sunny.

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Tingler Lake – the centerpiece of Tingler Prairie Natural Area.

We never did find the trillium—even calling another friend (Casey), who had seen them here before to find out exactly where he saw them. Turns out we hit the right spot, but apparently we were too early, especially given how late spring has been moving along this year. Nevertheless, we still found much to capture our interest, including a yellow-bellied racer (Coluber constrictor flaviventris)—too quick for photos—and a black rat snake (Pantherophis obsoletus) that coiled up nicely under the end of a fallen log and tolerated my prodding and “cleaning” of the scene around him to get some good photos (albeit, only with the iPhone).

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Black rat snake (Pantherophis obsoletus).

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The “cloudy” eye is actually an artifact of the flash lighting reflected by the retina.

Unfortunately, insect activity was very light. We saw no tiger beetles and only the earliest spring forms of most other insects. I took about 10 specimens each of the early-spring jewel beetles Acmaeodera tubulus and Pachyschelus purpureus, which I found on flowers and foliage (respectively) of wild geranium, Geranium maculatum. It was the first time that I’d found the latter as abundant as this, so the series of specimens will be a welcome addition to my cabinet. I also took a couple of A. tubulus on a flower of violet wood sorrel, Oxalis violacea and showed the others the characteristic end of an oak twig pruned by a twig pruner (Anelaphus parallelus) larvae (and revealed the culprit for them to see). Despite the paucity of insects, it was a beautiful and high-quality spot, and I look forward to collecting here again sometime when the season is more advanced.

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Several adult Acmaeodera tubulus feeding on petals of wild geranium (Geranium maculatum) flowers.

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Twig pruner, Anelaphus parallelus, larva cut from its gallery near the base of a pruned oak twig.

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Revealing the culprit while Chris takes notes on some of the birds he’s been hearing.

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Redspotted purple butterfly, Limnetis arthemis astyanax (family Nymphalidae), caterpillar on black cherry (Prunus serotina), one of its favorite host plants. The caterpillar mimics bird droppings for protection.

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Fire pink, Silene virginica (family Caryophyllaceae) thrives on a dry, cherty hillside.

Mayapple, Podophyllum peltatum (family Berberidaceae) prefers the rich, more mesic hillsides (this is where we expected Trillium viridescens to occur).

After finishing up at Tingler Prairie, we drove east an hour and bushwhacked over rough Forest Service 2-track to Bald Hill Glade Natural Area in Ripley Co. It had been close to 10 years since my previous visit, but I remembered the roads well. We had to park, however, about a mile from the entrance to the glade due to fallen trees across the final stretch 2-track. The landscape had changed considerably since my last visit—gone was the dense, close forest lining the 2-track, and in its place stood open woodland brought to this condition by active management that included the use of prescribed burning apparently as recently as the past season.

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Patches of the relatively rare dwarf iris, Iris cristata (family Iridaceae) growing on rich, wooded hillsides as we approached the glade.

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Dwarf iris (Iris cristata) is distinguished from other members of the genus by its short stature and sepals with midline beards.

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Bald Knob Glade Natural Area.

After hoofing through the forest we reached the glade and found a beautiful—if somewhat sterile—scene before us. The recent burn included not only the woodland but also the glade itself, and no unburned refugia could be found anywhere. Floristically, this is beneficial for the glade, which needs periodic fire to prevent woody encroachment, but in my experience such burns also result in severely depressed insect populations for years afterwards. It takes time for the insects to find and recolonize the glade, and in this case the lack of unburned refugia will only increase the amount of time that will be needed for the insect populations to recover.

Nevertheless, we enjoyed our hike through the area, watched and listened to the calls and songs of a number of cool birds, including summer tanagers, indigo buntings, blue-gray gnatcatchers, and—a first for me—the splendidly yellow prairie warbler. We also took photographs of the glade and some of its plants (with the big camera), and on the way back to the car we found several of the Polistes wasp-mimicking light flies, Pyrgota undata (family Pyrgotidae). Interestingly, all were mating pairs, and the ones we observed closely (as we photographed them with the big camera) were engaged in a most curious “French kissing” behavior. I can’t wait to read up more on this when I prepare to post the photos of this behavior.

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Widowscross, Sedum pulchellum (family Crassulaceae) colonizes the rocky dolomite exposures.

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Widowscross (Sedum pulchellum) getting ready to bloom.

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Me, Rich, Bill, and Chris.

Eventually, impending dusk signaled a close to the day, and after driving east another 1½ hours to have pizza dinner in Poplar Bluff we made the long drive back to St. Louis (arriving at my home at 12:30 a.m.!).

NOTE: All photos in this post were taken and processed with an iPhone X. The “real” photos taken with our “real” cameras will be shared as they become available.

© Ted C. MacRae 2019

Posted in Berberidaceae, Buprestidae, Caryophyllaceae, Cerambycidae, Coleoptera, Crassulaceae, Geraniaceae, Iridaceae, Nymphalidae, Reptilia, Vertebrata | Tagged , , , , , , , , , , , , , , , , , | 12 Comments

When hardcore botany meets hardcore nature photography—nature geekery at its finest!

Last Saturday, the Webster Groves Nature Study Society (WGNSS) Nature Photography Group was joined by several members of the WGNSS Botany Group and Missouri Native Plant Society to look for one of Missouri’s rarest plants—Geocarpon minimum, a.k.a. tinytim or earth-fruit (family Caryophyllaceae). This diminutive, federally-threatened and state-endangered plant grows only on sandstone glades, primarily in west-central Missouri with a few populations known also from Arkansas, Louisiana, and Texas. The window for finding this plant is short—it’s entire life cycle lasts only about 4 weeks, with an even shorter window for finding it in flower.

Our first stop to look for them was Bona (pronounced “Bonnie”) Glade Natural Area. I’d been here before, but it was about 10 years ago and at the wrong time to look for this plant (but I did find widowscross, Sedum pulchellum, in bloom). Some of the group had seen it here before and were able to coach us on the microhabitat where we would likely find them, and it didn’t take long before we did. Soon after finding the first plants, we found them in bloom as well—their almost microscopic flowers being the perfect subject for my macro lenses!

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Remnant sandstone glade at Bona Glade Natural Area, Dade Co., Missouri.

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Geocarpon minimum (tinytim or earth-fruit). Note the tiny open flowers just below center. (This is an iPhone photo—I have much better photos with my “big” camera.)

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Claytonia virginica (spring beauty) (family Montiaceae).

After getting plenty of shots of the plant and flowers, we moved to an adjacent plot of land across the highway, where we not only found more tinytim plants but also Corydalis aurea, commonly called golden corydalis (pronounced koor-ID-uh-lyss), in the family Papaveraceae—something I’d never seen before.

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Sedum pulchellum (widowscross) (family Crassulaceae).

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Corydalis aurea (golden corydalis).

Next the group moved on to Corry Branch Glade. It was originally our intent to look for more of the plant at this site, but immediately upon entering the glade we noticed a stunning display of Selenia aurea, or golden selenia. This small, striking species in the mustard family is restricted to just a handful of counties in the west-central part of the state, again primarily glade habitats. It was a surprising and pleasant find that occupied the groups’ attentions for some time before we finally decided to break for lunch (it was well into the afternoon!). While I was there, I not only photographed the plant but started having some success with my new 15-mm wide-angle macro lens, with which I had been experimenting all day (to that point without much success).

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Selenia aurea (golden selenia) (family Brassicaceae).

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Members of WGNSS & MoNPS go hunting for rare plants! Front to back: Ted MacRae (me), John Oliver, Casey & Anh Do Galvan, Steve Turner, Bill Duncan, David Seidensticker, Deb Tyler, Adam Rembert, and James Faupel.

After “lunch” (which was closer to dinner!), a few of us (Bill, David, and I) wanted to go back to Bona Glade to take another crack at photographing tinytim with our wide-angle macro lens. I especially was not satisfied with what I had gotten earlier, that being my first serious attempt at using the lens in the field. Having a better idea now of how to use the lens and what our compositional goals were, we scoured the area looking for just the right plants in just the right situations. I can honestly say I finally got a feel for how to use the lens, the trickiest part of it being how to balance use of flash on the subject with the amount of ambient light from the background (I’m not a stranger to this concept at all, frequently having combined flash with “blue sky” in much of the macrophotography I’ve done up to this point). We photographed several plants on different substrates looking for the right combination of plant, substrate, and background, and we all walked away pretty optimistic that we’d gotten the photos that we wanted.

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Bill Duncan photographing tinytim with his wide-angle macro lens.

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Amelanchier arborea (serviceberry) (family Rosaceae).

My thanks to Casey and Ando Galvan for letting me ride down there with them, to David Seidensticker and Bill Duncan for letting me ride back with them, and for everyone in the group who so generously shared their great, collective knowledge of botany, photography, and natural history. What a fun day!

NOTE: The photos in this post were taken with an iPhone X. The “real” photos, taken with our “real” cameras, will be shared as they become available.

© Ted C. MacRae 2019

Posted in Brassicaceae, Caryophyllaceae, Crassulaceae, Montiaceae, Papaveraceae, Rosaceae | Tagged , , , , , , , | 2 Comments

2019 WGNSS Nature Photo Contest

Last night the Webster Groves Nature Study Society (WGNSS) held their 2019 Nature Photo Contest, and I was fortunate to have a 1st place winner in the ‘Plants and Fungi’ category! This photograph of grassleaved lady’s tresses orchid (Spiranthes vernalis) flowers was taken at Taberville Prairie Natural Area in St. Clair Co., Missouri. Like other species of lady’s tresses orchids, their tubular flowers are arranged in a spiral along the inflorescence and cross-pollinated primarily by long-tongued bees (e.g. bumblebees, Bombus spp., and megachilid bees) (van der Cingel 2001).

Spiranthes vernalis (spring lady's tresses)

Grassleaved lady’s tresses orchid (Spiranthes vernalis), Taberville Prairie Natural Area, St. Clair Co., Missouri.

Spiranthes is one of the more complex genera of North American orchids, with seven species known to occur in Missouri (Summers 1985), and like almost all orchids, their pollination biology is fascinating! The flowers are “protandrous”, i.e., they are functionally male when they first open and become functionally female as they age. Since they open sequentially from the base of the inflorescence as it grows, this results in female flowers on the lower portion of the inflorescence and male flowers on the upper portion.  Thus, bee pollinators tend to act as pollen donors when visiting lower flowers and pollen recipients when visiting upper flowers.  Male pollinia are attached to the bee’s proboscis as it tries to access the nectar secreted into the base of the floral tube and then come in contact with the female stigma in the next flower that the bee visits.  Bees generally start at the bottom of an inflorescence when visiting a plant and then spiral up to the top before flying to the next plant.  Such “acropetal movement” is likely a result of the tendency for nectar rewards to be greater in the lower flowers, and it ultimately promotes cross-fertilization between neighboring plants.

This was the 4th edition of the contest, which has been held every other year since the inaugural edition in 2013. I’ve earned 2nd and 3rd place honors in the plants category each time before; however, this was my first win in that category. In addition to plants, I also had entries in the ‘Invertebrates’ (restricted to photos taken in Missouri or one of its contiguous states) and ‘Travel’ (open to photos taken anywhere in the world) categories, with one photo each making it to the final round of judging. You’ve seen them both before—Neotibicen superbus (below left—photographed at Mincy Conservation Area, Taney Co., Missouri) and Agrilus walsinghami (below right—photographed at Davis Creek Park, Washoe Co., Nevada). In the end, however, they both got beat out by the competition, so I only had the one winning photograph this time. Nevertheless, it was a 1st place winner, so I am very satisfied.

The WGNSS Nature Photo Contest has quickly become one of the organization’s marquee events, with the number of entries, caliber of competition, and attendance all exceeding the previous three editions. My thanks to the judges who volunteered their time, the attendees who supported the event, and especially to Bill Duncan, Chair of WGNSS’s Nature Photography Group (and an expert nature photographer in his own right), who worked hard to make this event the success that it was (and took home some well-deserved wins of his own). I look forward to the next competition in 2021!

REFERENCES:

Summers, B.  1981.  Missouri Orchids.  Missouri Department of Conservation, Natural History Series No. 1, 92 pp.

van der Cingel, N. A.  2001.  An Atlas of Orchid Pollination: America, Africa, Asia and Australia. A. A. Balkema, Rotterdam, Netherlands, 296 pp.

© Ted C. MacRae 2019

Posted in Buprestidae, Cicadidae, Coleoptera, Hemiptera, Orchidaceae, Plantae | Tagged , , , , , , , , , , , , , | 4 Comments

T.G.I.Flyday—Black horse fly (Tabanus atratus)

In my previous post, I talked about a day trip to a sand scrub remnant in the Lake Wales Ridge of central Florida to find and photograph the endemic Highlands tiger beetle (Cicindelidia highlandensis). Ironically, the dry sand scrub/pine woodland habitats along this ridge are dotted with small lakes and ponds, allowing a rich aquatic flora and fauna to co-exist alongside the xeric specialists. Field mate Chris Brown and I had found and just finished photographing the tiger beetles when we encountered this rather largish lake—bright, white sand surrounding crisp, clear water reflecting white, puffy clouds in a deep, blue sky. ‘Twas a spectacular sight, indeed!

Sand scrub lake

Sand scrub remnant, Lake Wales Ridge, central Florida

As we stood looking at the scenery, I noticed something black on the stem of one of the sedges growing along the water’s edge. Something big and black! As I moved closer I could tell quickly that it was a large horse fly, but it was not simply perched and resting on the sedge—there was something else going on. Moving closer, ever so cautiously so as not to disturb the fly, I eventually realized that it was a female in the act of oviposition. How cool—I’d never witnessed this before with any species of horse fly, so to see it with such a large species was a real treat. I recognized it instantly as Tabanus atratus—commonly called the black horse fly and recognizable as such by its large size, all-black coloration, and distinctively hooked antennae (see 3rd photo below).

Tabanus atratus ovipositing

A Tabanus atratus female oviposits on a stem overhanging the water.

Before we get to the eggs, let’s dispel some misinformation that seems to persist regarding the size of this species (as it does with almost any large insect). Black horse flies are undeniably large, and in fact they are one of the largest horse flies in North America. The more credible sources (e.g., Pechuman et al. 1983, Long 2001) cite body length as ranging from 20–25 mm (up to a full inch in length). Incredibly, the species does not take the honors as North America’s largest horse fly, which goes instead to Tabanus americanus and it’s upper limit of 30 mm (in fact, T. americanus may be the world’s largest horse fly)! There are, however, on-line sources and a few popular field guides (as cited in BugGuide) that state a maximum length of 28 mm for T. atratus. How credible this figure is I cannot say, but I guarantee that the size indications of 30, 40, and even a whopping 50 mm in length found routinely among photos of this species on BugGuide were not derived from careful measurement and almost certainly instead reflect the astonished reactions that such an abnormally large insect can generate! In fact, there are precious few insects in North America that reach lengths as grand as 50 mm (i.e., two full inches)!

Tabanus atratus ovipositing

Lateral view of oviposition.

We approached carefully, again so as not to disturb the female in the middle of her act, and we watched and photographed as she laid the individual eggs one by one, using the tip of her abdomen to carefully arrange them neatly against each other in stacked layers. From a photographic perspective, balancing flash exposure of the all-black adult with the bright-white egg mass presented a real challenge. Added to that was an additional exposure challenge (my desire for a blue-sky background), making it a truly difficult-to-photograph subject. Long (2001) states that T. atratus egg masses can contain anywhere from one hundred to a thousand eggs each, always near water’s edge or somewhere quite close to water. Females are capable of laying three or four of these egg masses, which apparently gradually turn dark as the eggs develop and approach hatch.

Tabanus atratus egg mass

Freshly laid Tabanus atratus egg mass.

Despite this being the first time I’ve ever witnessed oviposition by this species, it seems to be encountered regularly. There are several photos of ovipositing females among the many photos of this species that have been posted to BugGuide. Moreover, descriptions of the egg mass of T. atatus appeared very early in the literature, first by Hart (1895) and then in photographs by Schwardt (1936). The latter author also states “T. atatus deposits its eggs in masses which are so constant in structural plan as to make specific determination of the egg mass readily possible” (as quoted in Bailey 1948). Thus, even if this female had already finished and left her egg mass, it still could have been identified to species.

REFERENCES:

Bailey, N. S. 1948. Notes on Tabanus atratus subsp. nantuckensis Hine (Diptera). Psyche 55(3):131–138 [pdf].

Hart, C. A. 1895. On the entomology of the Illinois River and adjacent water. Illinois State Laboratory of Natural History Bulletin 4:149–273 [eBook].

Jones, C. M. & D. W. Anthony. 1964. The Tabanidae (Diptera) of Florida. U.S. Department of Agriculture, Agricultural Research Service, Technical Bulletin No. 1295, 85 pp. [pdf].

Long, W. 2001. Tabanus atratus (on-line), Animal Diversity Web. Accessed 20 March 2019 at https://animaldiversity.org/accounts/Tabanus_atratus/

Pechuman, L. L., D. W. Webb & H. J. Teskey. 1983. The Diptera, or true flies, of Illinois 1. Tabanidae. Illinois Natural History Survey Bulletin 33(1):1–121 [pdf].

Schwardt, H. I. 1936. Horseflies of Arkansas. Arkansas Agricultural Experiment Station Bulletin 332:14–15, 27–32.

© Ted C. MacRae 2019

 

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