An irresistible sight!

One of the few highlights of my Memorial Day weekend collecting trip came in the earliest moments of my visit to Ha Ha Tonka State Park.  My destination was Ha Ha Tonka Savanna Natural Area, and a short walk through fire-restored woodland led me to the open glade where just a few years earlier a UMC student had collected the rare and little-known Agrilus impexus.  Entering the glade, I was all set to begin sweeping the vegetation along the woodland/glade interface, paying special attention to any honey locust (Gleditsia triacanthos) that I might happen to find in the area as a potential host for the beetle.  What I saw instead as the glade opened up in front of me was a sight that any collector of wood-boring beetles will find almost irresistable – a recent wind-throw!  In this case, it was a black oak (Quercus velutina) laying in full sun – its bright brown leaves suggesting that it had fallen within the past few weeks (and would thus still be emitting the volatiles that wood-boring beetles find so attractive).  I wanted to begin looking for A. impexus, but I knew there would be beetles actively crawling on the trunk and branches of that tree.  I couldn’t resist it – I dropped my sweep net and beating sheet and made my way to the tree (in the end it didn’t matter, since no other beetles – including A. impexus – would be seen that day).

I already had an idea what I might find.  Recent wind-throws are the domain of Chrysobothris, and if the tree is a deciduous species then this means members of the Chrysobothris femorata species-group.  I recently featured one of six newly described members (C. caddo) of this taxonomically challenging group (Wellso and Manley 2007), providing a synopsis of the now twelve species in the group and their primarily host preferences.  Fully half of these are associated primarily or exclusively with oaks four occurring in Missouri (quadriimpressarugosiceps, shawnee, and viridiceps).  Of these, C. quadriimpressa is the most commonly encountered (although the others are by no means uncommon), and all of the nearly dozen or so beetles I found on this particular tree in fact represented that species. Confirmation of my ID would require microscopic examination of the female pygidium (which is shallowly impressed on each side of the middle) and male genitalia, but in general this species can be distinguished in the field by its smallish size (~10-12 mm in length – rugosiceps and shawnee tend to be larger) and the post-median pair of foveae (circular impressions) on the elytra being joined (they are distinctly separated in viridiceps).

As we’ve seen with other species of jewel beetles (e.g., C. caddo, Dicerca lurida, D. obscura), adults of C. quadriimpressa are incredibly cryptic and nearly impossible to see on the bark of their hosts – at least until they move.  They are notoriously difficult to approach – their large eyes and penchant for rapid escape flights suggesting excellent vision.  This is a useful capability for insects that must expose themselves to would-be predators (and beetle collectors) during daylight hours while actively searching dead trees for mates and oviposition sites.  One thing I can’t figure out, however, is the role of the intensely blue feet in this and other cryptically colored Chrysobothris species (see also C. caddo).  Any ideas?

Photo Details (insect): Canon 50D (ISO 100, 1/250 sec, f/16), Canon 100mm macro lens w/ Kenco extension tubes (68mm), Canon MT-24EX flash (1/4 ratio) w/ Sto-Fen diffusers.  Post-processing: levels, unsharp mask, minimal cropping.

REFERENCES:

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 Moth and Me #11

The Moth and MeWelcome to issue #11 of The Moth and Me, the monthly carnival devoted to the “forgotten” lepidopterans. Most people – even entomologists – regard these as the lesser leps, denizens of the night, as if to hide their somber-colored drabness from the flashy brilliance of their rhopaloceran relatives. Of course, this simply isn’t true, as the contributions to this month’s issue well demonstrate. Butterflies may be among the largest insects on earth, but the largest lepidopteran in the world is a moth. They may also be as gaudily colored as the rainbow itself, but what butterfly is more colorful than the Urania day-flying moths (the genus name literally means, “The heavenly one”).   And, they may be almost universally accepted by a largely insect-indifferent public, but who among us does not think back to that first sight of a luna moth as the most stunning insect we had ever seen to that point.  Yes, moths are all that butterflies are, and for this month’s issue of TMaM, 15 contributions by nine writer’s show us why.

Family Saturniidae – Giant Silkworm & Royal Moths

Tales from the Butterfly Garden: LepcuriousLuna moths belong to the royal moths of the family Saturniidae, and as the name implies they are not the only stunningly beautiful member of the group. Kristen at Tales from the Butterfly Garden: Lepcurious writes about an encounter with the Sweetbay Silkmoth (Callosamia securifera).  Like other members of the family, larvae of this species are rather particular about the type of tree that they utilize for food, which in the case of this moth is sweetbay (Magnolia virginiana).  I’m a little too far north here in Missouri for this tree, so I have never seen this moth.  However, I have seen (and reared) some of its close relatives, the Promethia Silkmoth (Callosamia promethea) which hosts on several plant species and the Tulip-tree Silkmoth (Callosamia angulifera) which hosts on Tulip Tree (Liliodendron tulipifera).

Family Zygaenidae – Leaf Skeletonizer Moths

xenogereJason Hogle at xenogere is fond of the unusual and has a gift for finding it. In his post The Unmoth, Jason shows us a male grapeleaf skeletonizer (Harrisina americana) – not your typical moth!, The uniformly black color and bright red neck collar just screams “Don’t eat me – I’m poisonous”, and indeed species in this family are among the few insects capable of producing hydrogen cyanide!  As the name suggests, larvae skeletonize the leaves of both wild and cultivated grapes (Vitis spp.), as well as the related Virginia creeper (Parthenocissus quinquefolia).

Family Noctuidae – Noctuid Moths & Tiger Moths

Tales from the Butterfly Garden: LepcuriousRoyal moths are not the only stunningly colored moths that Kristen at Tales from the Butterfly Garden: Lepcurious has found in Florida, as she shows in this post on Oleander Moths (Syntomeida epilais) and a companion piece on its Oleander host plant.  This striking day-active moth, also called Uncle Sam Moth (for its red, white, and blue colors) and Polka-Dot Wasp Moth (for obvious reasons), may seem like an easy-to-spot target for would be predators, but its gaudiness is actually warning of the toxic chemicals it has sequestered in its body from the Oleander on which it fed as a larva.  Oleander contains the toxins oleandrin, a cardiac glycoside, and neandrin and is toxic if ingested.  Although oleander is an Old World exotic, oleander moths may also be found feeding on devil’s potato vine (Echites umbellata), which may have been their native Florida host before the introduction of oleander to the United States.

See TrailAside from the underwings (genus Catacola) and the recently incorporated tiger moths, Noctuids are typically thought of as the “basic brown moths” – relying on just the aforementioned groups to add a splash of color to the family’s otherwise drearyness.  Nothing could be further from the truth – check out the stunning Eight-spotted Forester (Alypia octomaculata) in this post by Matthew York at See Trail. Larvae of this beautiful little moth feed on ampelopsis, Virginia creeper, and other plants in the grape family (similar to the grape leaf skeletonizer above). “A great moth; brilliant color, diurnal…… and yes… Noctuid. Some moths, like people, don’t go with the trends.”

See TrailFor the most part, tiger moths shun the daytime in preference for the safety of the night. That does not mean, however, that they are any less colorful, as Matthew York at See Trail shows in his post Poor Grammia. Notarctia proxima, the Mexican Tiger Moth, and its relatives have had a bit of name shuffling over the years at the hands of taxonomists – formerly placed in the genera Grammia and Apantesis. Whatever name you call it, the striking white and black striped forewings give a clue about their common name of tiger moths, and the red, black-tipped abdomen not only add to its beauty, but belies the defensive compounds it surely contains.

Speaking of tiger moths and defensive compounds, watch the video that Chris Grinter at The Skeptical Moth included in his post Moth Perfume. In it, Chetone angulosa gives a striking display of a common defensive mechanism for the group – excreting hemolymph (sweating blood, so to speak!). So spectacularly does the moth do this that you can actually hear the hissing sound of the fluid being pumped from the body. Moreover, there seem to be at least a couple of active ingredients in the froth – one that smells like peppermint, and another that causes numbing of the tongue (as Chris can testify firsthand – he is a truly dedicated experimental naturalist!).

Karthik's JournalIn similar fashion to our North American species of underwing moths (Catocola spp.), the related Eudocima materna, one of the fruit-sucking moths of south India, uses its drab-colored forewings to hide its brilliantly colored hindwings, as Karthik at Karthik’s Journal shows us in his post Startling Displays.  This forms a double line of defense against would-be predators – the forewings blend marvelously into the color of the tree trunks upon which it rests during the day, camouflaging the insect and making it nearly invisible.  If this doesn’t work, a sudden flash of the hindwings may startle the predator just enough to allow the moth to take flight to another tree – where it instantly “disappears” as soon as it closes its wings.

Snails Eye ViewAustralia also has some very colorful fruit-piercing moths, and Bronwen Scott at Snails Eye View presents some beautiful photos of the particularly strikingly-colored Othreis iridescens. Like other members of the group, this Far North Queensland endemic feeds on fruit (Pycnarrhena novoguineensis and Hypserpa laurina, both Menispermaceae, in the case of this species), but as it is apparently the rarest of the primary fruitpiercing moth species in Australia it is not considered to be a pest (and Bronwen would cut it some slack even if it was!).

EntophileAdults are but only one of four life stages that all moths go through. If moths are the “forgotten” leps, then caterpillars are the “forgotten” moths. In many cases, the caterpillar stage cannot be recognized until it becomes a moth (and in some cases the caterpillars are completely unknown). Fortunately, Navy entomologist corycampora at Entophile recognized the caterpillar he found on his croton bush, which he features in the post Croton caterpillar, Achaea janata (Linnaeus), (Lepidoptera: Noctuidae). These “eating machines” can be just as fascinating to observe as their scaled adult counterparts, and while croton seems to be a preferred host in Hawaii, it apparently also feeds on castor beans (judging by its other common name, Castor Oil Semi-looper).

Family Notodontidae – Prominent Moths

the Marvelous in NatureOften dismissed as noctuids, the prominent moths tend to be fuzzier, more thickly-bodied moths that rest with their wings curled around their abdomen or tented over their back (rather than flat like noctuids and most other moths). TMaM organizer Seabrooke Leckie at the Marvelous in Nature has a love affair with prominents, and in her post Georgian Prominent, she features the nicely thick-bodied and fuzzy Georgian Prominent, Hyperaeschra georgica. The caterpillars of this widespread species feed on oak (Quercus spp.), thus, unless you live in the Pacific Northwest you stand a good chance of encountering this species – if you’re you’re willing to make the effort.

Family Psychidae – Bagworm Moths

xenogereMany of us are probably familiar with the evergreen bagworm moth (Thyridopteryx ephemeraeformis), whose large, cone-shaped bags almost look like fruit hanging from the evergreen bushes on which the caterpillars feed. But did you know there are other species of bagworms as well? Jason Hogle at xenogere does, and he compares and contrasts two of them in this duo of posts, Rainy day on the patio and The Other Bagworm. One huge and prominent, the other (Dahlica triquetrella) very small and oft unseen. One with all manner of plant matter stuck to its bag, the other usually mistaken for small bits of dirt or wood. Jason is so good, he can even determine the sex of the caterpillar inside the bag!

Family Sphingidae – Hawk Moths

Roundtop RumingsCarolyn at Roundtop Rumings is hoping that somebody can Name this moth, which she found on the door of her cabin in the forests of Pennsylvania. Don’t let her inability to name this moth fool you, however, for her post contains loads of information on exactly the kinds of characters one should take note of when trying to identify hawk moths. Large size and membership in a popularly studied group aren’t enough – what do the hindwings look like? Are there any spots on the abdomen? As a coleopterist, I hesitate to offer my relatively uninformed opinion on the exact genus and species for this moth, but I’m going to go out on a limb here and suggest maybe something in the genus Ceratomia, perhaps the waved sphinx (C. undulosa)?


I hope you have enjoyed this issue of The Moth and Me, and my sincere thanks go out to all of those who contributed!  The hosting slot for next month’s issue of TMaM is still open, but you can submit your contributions anyway to Seabrooke Leckie at the home site for inclusion in the June 2010 issue once a host is selected.  The submission deadline is June 13, with the issue appearing a few days later.  Perhaps you might like to host the June issue – hosting is not only fun, but also a great way to introduce readers to your site and generate a little traffic.  Contact Seabrooke at the home site if you’re interested – I’m sure she would love to hear from you.

Copyright © Ted C. MacRae 2010

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Monday Moth – Trichaeta pterophorina

 Trichaeta pterophorina – Borakalalo National Park, South Africa

Another photo from the South Africa files, and one that continues the mimicry theme that has been featured in several recent posts. It’s not a great photograph – the focus is off – but the colors these moths sport are dazzling, and there is a nice symmetry to their tail-to-tail mating position.

Roy Goff, author of the website African Moths, tells me this species is the Simple Maiden (Amata simplex) in the family Arctiidae (whose ~2,000 species worldwide are increasingly considered a subfamily of the already enormous Noctuidae) [update 6/20/2012—Martin in a comment considers these moths to actually represent Trichaeta pterophorina in the same subfamily].  Its gestalt – greatly resembling a stinging wasp – brings to mind the so-called “wasp moths” of North America (subtribe Euchromiina); however, maidens belong to the exclusively Old World Syntomina.  Like the wasp moths, most maidens are exceptionally colorful and exhibit clearly aposematic patterns.  While these might seem to be textbook examples of Batesian mimicry, most species in this group are also protected by distasteful secondary plant compounds that they sequester through feeding, making them Mullerian rather than Batesian mimics.  These compounds are not only acquired by larvae from their food plants, but also by adult moths who imbibe them from fluid regurgitated through their proboscis onto dried parts of plants containing the compounds and into which they dissolve.

Their aposematism is not limited to strictly visual cues.  An Australian species, Amata annulata, is known to regularly emit ultrasonic clicks when flying, thought to be aposematic behavior to warn bats of its distastefulness in the same way that that its coloration warns daytime predators. Additional defensive characters that have been described for species in the group include frothing and extrusion of defensive processes. Clearly, maidens are leaders in the arms race among the insects!

Copyright © Ted C. MacRae 2010

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Pseudomethoca simillima – a model for Enoclerus ichneumoneus?

Pseudomethoca simillima (family Mutillidae) - the model?

Enoclerus ichneumoneus (family Cleridae) - the mimic?

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

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

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

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

REFERENCE:

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

Copyright © Ted C. MacRae

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Orange-banded checkered beetle

As a student of woodboring beetles for more than a quarter-century now, I’ve had occasion to encounter a goodly number of checkered beetles (family Cleridae) – both in the field and as a result of rearing them from dead wood.  Checkered beetles are not as commonly encountered as other woodboring beetle families such as Buprestidae and Cerambycidae, and they also generally lack the size, diversity, and popularity with coleopterists that those aforementioned beetle families enjoy.  However, despite these shortcomings as a group, checkered beetles are among the most brightly colored and boldly patterned of beetles.  Unlike the beetles with which they often found, checkered beetles are not actually themselves woodboring beetles, but rather predators of such (particularly bark beetles in the weevil subfamily Scolytinae).

This particular species, Enoclerus ichneumoneus, is one of the more conspicuous members of the family in eastern North America.  Although the genus to which it belongs is the largest of the family (32 species in North America north of Mexico), the wide orange band across the middle of the elytra and elongate scutellum make this species distinctive and unlikely to be confused with any other.  I found this individual along the Ozark Trail in southern Missouri on a recently fallen mockernut hickory (Carya alba) – a number of other adult buprestid and cerambycid species were also found on this tree, all of which were mating, searching for mates, or laying eggs within the cracks and fissures on this new-found resource.  In the past I have encountered large numbers of adults of this species on dead willow (Salix caroliniana) from which I later reared an even larger number of a small willow-associated buprestid, Anthaxia viridicornis.  Whether the buprestid larvae served as prey for E. ichneumoneus is difficult to say, but no other potential prey beetle species were reared from the wood.

The bright, distinctive colors exhibited by many checkered beetles might seem to suggest aposematic, or warning, coloration to discourage predation; however, the question of checkered beetle palatability to predators has not been adequately studied (Mawdsley 1994).  The colors and patterns of many species, especially in the genus Enoclerus, seem to mimic species of velvet ants (family Mutillidae) and true ants, but other beetles (e.g. species of Chrysomelidae and Tenebrionidae) and even flies have also been suggested as models.  Still other checkered beetle species seem to be more cryptically than mimetically marked, and there are several tribes whose members seem to be chiefly nocturnal and are thus mostly somber-colored.

Of the 37 genera occurring in North America north of Mexico, I have in my collection representatives of more than 100 species in 23 of those genera.  The majority of that material has been reared from dead wood collected for rearing Buprestidae and Cerambycidae – much of it coming from Texas and Arizona as well as here in Missouri.

Photo Details: Canon 100mm macro lens on Canon 50D, ISO 100, 1/250 sec, f/14, MT-24EX flash 1/4 power w/ Sto-Fen diffusers, photo lightly cropped.

REFERENCE:

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

Copyright © Ted C. MacRae

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Mylabris oculatus in South Africa

Mylabris oculata, the CMR bean beetle, is a large, conspicuously-colored beetle in the family Meloidae (blister beetles) that I saw quite commonly during my stay in South Africa.  “CMR” refers to the Cape Mounted Rifle Corps, a police force in the old Cape Colony whose uniforms sported black and yellow bands that resemble the colors of this beetle.

Blister beetles as a whole are, of course, well known for their chemical defenses, primarily cantharidin (the active ingredient in ‘Spanish Fly’, an extract of a European species of blister beetle).  This terpenoid compound is a painful irritant, especially when coming into contact with mucous-lined membranes such as those of the gatrointestinal and urinary tracts.  Blister beetles emit body fluids containing cantharidin from joints on the legs when disturbed, giving any would-be predators a foul-tasting appetizer. As we have so often seen, insects containing such effective defenses are often aposematically colored to advertise the fact, allowing them to brazenly lumber about fully exposed during the day with little to fear.  If there ever was an insect that screamed aposematic, it is M. oculatus with its boldy contrasting black and yellow elytra and hot-orange antennae.

These beetles, however, are more than just a frustration for hungry birds, but also a serious pest of numerous ornamental, fruit and vegetable crops (Picker et al. 2002).  Large numbers of adults congregate on plants and preferentially feed on the flowers.  In the more natural settings where I was encountering these beetles, they were most often seen on flowers of Acacia spp. or (as in the above photo) Dichrostachys cinerea in the family Fabaceae.  To be honest, they became quite a source of frustration for me as well – not because of their distastefulness or pestiferous habits, but because of their role as the model in a mimicry complex.  It was the mimic that I was after, and since mimics tend to be much less common than their models, I had to look at a lot of M. oculatus to find the few specimens of the species I was after. 

Pop quiz: Can anybody name the mimic?

Back to their chemical defenses – I’ve often wondered just how poisonous blister beetles really are, especially to humans.  Here in the U.S., their main importance is as contaminants in alfalfa hay fed to cattle and horses.  Deaths from severely contaminated forage do occur, but this is dependent upon the cantharidin content of the species and their abundance within the hay.  The highest reported cantharidin content for a blister beetle is 5.4% dry weight in Epicauta vittata.  Calculations based on this figure and the lethal dose for a 1000-lb horse indicate that around 100 such beetles would need to be eaten to receive a fatal dose.  This seems to make the claim that a single beetle can kill a human a little far-fetched.  However, M. oculatus are big beetles – more than a full inch in length and bulky.  In this regard, I found an interesting tidbit at the TrekNature website.  Clarke Scholtz is an entomologist at the University of Pretoria, and when asked, “Is it true that their poison can kill a human being?”, he responded:

Yes; they are poisonous enough to kill people – especially a big beetle… The poison is very toxic and actually causes collapsed tissue. It would also depend on the weight of the person, as with any other toxin. The poison of a CMR beetle, that is dried and powdered, is sufficient to kill a 70kg human.

REFERENCE:

Picker, M., C. Griffiths and A. Weaving. 2002. Field Guide to Insects of South Africa. Struik Publishers, Cape Town, 444 pp.

Copyright © Ted C. MacRae 2010

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Monday Moth: Arniocera erythropyga

Arniocera erythropyga (Zygaenidae), Geelhoutbosch, South Africa

Last week’s king cricket quiz (Tuesday Teaser) reminded me that I still have quite a few photographs from my trip to South Africa, now 10 years ago, that I still haven’t shared. This pretty little moth is Arniocera erythropyga, which I photographed at Geelhoutbosch farm in South Africa’s Northern (now Limpopo) Province while clambering up the magnificent north-facing escarpment of the Waterberg Mountains. 

I saw this moth as it sat on the foliage of Grewia sp. (family Malvaceae) – fully exposed for all the world to see.  If we’ve learned anything by now, we know that brightly colored insects that expose themselves conspicuously during the day are probably protected by chemical defences (or perhaps mimicking something that is). Such was the case for Bromophila caffra, an equally strikingly-colored fly that I saw on the same hike, and it is also the case for this moth as well. Arniocera erythropgya is a member of the family Zygaenidae, or burnet moths – many members of which are known to release hydrogen cyanide (Scholtz and Holm 1985). This is the same family to which another toxic species I featured last spring belongs (Pyromorpha dimidiata).  A number of moths and butterflies in other families are also known to release HCN (produced by the breakdown of cyanoglucosides sequestered from the plants on which they feed); however, all life stages of zygaenid moths, including the egg, contain these compounds.  This suggests that zygaenid species are capable of synthesizing these compounds themselves rather than needing to sequester them from their host plants (Scoble 1992). While some zygaenid larvae do feed on plants that contain cyanoglucosides, they apparently do so simply because of their tolerance to the compounds but without the need to sequester them from the plant.

Thus, when I saw and approached this little moth, it didn’t flinch or flee.  Protected by toxicity, it continued sitting brazenly atop its exposed perch – welcoming me to see it, daring me to do anything more than take its photo.

My thanks to Roy Goff at African Moths for confirming the identity of the individual in this photograph.

REFERENCES:

Scholtz, C. H. and E. Holm (eds.). 1985. Insects of Southern Africa. Butterworths, Durbin, South Africa, 502 pp.

Scoble, M. J. 1992. The Lepidoptera. Form, Function and Diversity. Oxford University Press, Oxford, 404 pp.

Copyright © Ted C. MacRae 2010.

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A Tiger Beetle Aggregation

Not long ago, I received an interesting series of photographs from Joe Warfel, a nature photographer and macro specialist based in Massachussetts.  Joe traveled to Arizona last July, where he photographed an aggregation of Cicindela (Cicindelidia) sedecimpuntata (Western Red-bellied Tiger Beetle¹) near a small pool in the bottom of a dry creek bed at night.  Joe estimates that there may have been as many as 200 to 300 beetles per square meter in the aggregation, most of which were just “hanging out” and with only occasional individuals mating or feeding on moths that had been attracted to his headlamps.

¹ Found in the Sonoran and Chihuahuan Deserts of the southwestern U.S. and south through Mexico to Costa Rica. U.S. and northern Mexican populations are assigned to the nominate subspecies, while more southern populations are classified into four additional subspecies (Erwin and Pearson 2008).

Western Red-bellied Tiger Beetles are among the first tiger beetles to appear prior to the summer monsoons in the Sonoran Desert.  The species is famous for its daytime aggregations of as many as several thousand individuals, which congregate along the drying waterways and prey upon stranded tadpoles and other aquatic organisms (Pearson et al. 2006).  Joe noted that he has seen these aggregations many times before during the daytime at small pools and mudflats, with beetles usually mating and feeding frantically.  However, the aggregation shown in these photographs differs from those daytime aggregations by the relative inactivity of the beetles and the fact that they were congregated on dry ground rather than the moist areas that they frequent during the daytime.  In these respects, it seems to more resemble a communal nocturnal roost such as has been reported for several species of Odontocheila in South America.  In those cases, up to 70 beetles have been found resting on the foliage of low shrubs, apparently as an adaptation to avoid predation by multiplying chemical defense effectiveness as well as awareness of approaching enemies (Pearson and Vogler 2001 and references therein).  Cicindela sedecimpunctata is primarily a diurnal species (i.e., it is active during the daytime), though individuals are often attracted to lights at night, and adults of most diurnal species have been reported spending the night protected in burrows or under detritus and vegetation.  I am not aware of communal nocturnal roosts as a reported behavior for C. sedecimpunctata or any other North American tiger beetle species.

It is a bit ironic to think of tiger beetles – voracious predators that they are – as prey, but they must have many of their own predators to deal with since most species employ multiple antipredator mechanisms. In addition to the communal roosting behavior seen in these photos, a second antipredator characteristic exhibited by this species can be seen in their bright orange abdomen.  The abdomen is fully exposed only during flight, seemingly implying a “flash coloration” function for the bright color that disappears upon landing, momentarily confusing potential predators.  However, Pearson (1985) experimentally determined that orange abdomens in tiger beetles actually have an aposematic function in protecting them from predation against robber flies.  Most tiger beetle species with an orange abdomen also release a combination of benzaldehyde and cyanide² when captured (any tiger beetle collector is familiar with the characteristic “fruity” smell of a tiger beetle releasing benzaldehyde).  Pearson painted the abdomen of paper tiger beetles models either orange or black and endowed them with or without a drop of fresh benzaldehyde.  When presented on a tether to robber flies in the field, orange-abdomened models with benzaldehyde triggered significantly fewer attacks from robber flies than any other combination.  Interestingly however, vertebrate predators (lizards and birds) were not deterred by the defense chemicals or by the orange abdomen, perhaps explaining why only some and not all tiger beetle species produce defense chemicals and have bright orange abdomens (Pearson and Vogler 2001).

² Tiger beetles, thus, join millipedes as being among the few invertebrates that are capable of producing cyanide.

My sincere thanks to Joe Warfel for allowing me to use his photographs. More of his work can be seen at Eighth-Eye Photography.  Joe also recently had several images published in American Scientist magazine (November/December 2009 issue) for an article on harvestmen.  Check out the jaws on that juvenile!

REFERENCES:

Erwin, T. L. and D. L. Pearson. 2008. A Treatise on the Western Hemisphere Caraboidea (Coleoptera). Their classification, distributions, and ways of life. Volume II (Carabidae–Nebriiformes 2–Cicindelitae). Pensoft Series Faunistica 84. Pensoft Publishers, Sofia, 400 pp.

Pearson, D. L.  1985.  The function of multiple anti-predator mechanisms in adult tiger beetles (Coleoptera: Cicindelidae).  Ecological Entomology 10:65–72.

Pearson, D. L., C. B. Knisley and C. J. Kazilek. 2006. A Field Guide to the Tiger Beetles of the United States and Canada. Oxford University Press, New York, 227 pp.

Pearson, D. L. and A. P. Vogler.  2001. Tiger Beetles: The Evolution, Ecology, and Diversity of the Cicindelids.  Cornell University Press, Ithaca, New York, 333 pp.

Copyright © Ted C. MacRae 2010

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