Bon appétit!

I collected this larva in northwest Nebraska during last year’s Fall Tiger Beetle Trip.  I collected an adult Cicindela lengi (blowout tiger beetle) at the spot – a species that greatly resembles but is much less common than the ubiquitous C. formosa (big sand tiger beetle – see my post Cicindela lengi vs. Cicindela formosa for a comparison of the two species).  Before finally finding that adult, however, I had fished out several larvae from the site in the hopes that they represented that uncommon species (see how I did this in my post Goin’ fishin’).  After collecting the larvae and placing them in a small terrarium with native sandy soil, they burrowed in but then closed up shop – I wasn’t sure whether they had survived or not.  In early December I put the terrarium in a 10°C incubator for the winter and brought it back out earlier this month.  Yesterday, happily, this larva and one other opened up their burrows again, so with any luck I’ll feed them well and they’ll complete their development.  While I do hope they represent C. lengi, other possibilities include C. scutellaris (festive tiger beetle), which would not be exciting, and C. nebraskana (prairie long-lipped tiger beetle), which would be VERY exciting.  One species I do not have to worry about it being is C. formosa, as the larvae of that species make very unique excavations in the sand with the burrow opening directed towards the excavation (I don’t believe I’ve posted photos of that here, yet – I’ll have to do so soon).

In the meantime, here is a closeup of the larva in the video prior to feeding. Those of you who have ever reared or photographed tiger beetle larvae will know just how easily “spooked” these larvae can be – any sudden movement will cause the larva to “drop” into its burrow and sit there for awhile. As a result, it was a real challenge to go through the whole process of taking first the photos and then the video while feeding it without causing it to drop.

cicindela_sp_larva_p1020936

Coming soon – lunchtime for adults!

Copyright © Ted C. MacRae 2009

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Millipede assassin bug

Ectrichodia crux

I continue the hemipteran theme begun in the last post with this photograph I took in South Africa below the Waterberg Range in Northern (now Limpopo) Province. I recognized them as members of the family Reduviidae (assassin bugs), and since to my knowledge species in this family are exclusively predaceous (except for the so-called “kissing bugs” of the mostly Neotropical subfamily Triatominae, large distinctive bugs that feed exclusively on vertebrate blood), I found what I took to be a case of scavenging on a dead millipede to be rather curious.  It had rained the previous evening, resulting in a burst of millipede (and insect) activity that night, and this scene was rather commonly encountered the following morning. Of course, appearances can be deceiving, and it turns out that I actually was witnessing predation – and a most unusual case at that.  The individuals in this photo represent Ectrichodia crux (millipede assassin bug), a common species in many parts of southern Africa.  Although nearly 500 species of assassin bugs are known from the region (Reavell 2000), E. crux is easily recognizable due to its large size (adults measure up to 22 mm in length), stout form, and coloration – shiny black, with a distinctive black cross incised on its dull yellow thorax and with yellow abdominal margins (Picker et al. 2002). The nymphs as well are distinctive – bright red with black wing pads. Clearly, these insects are advertising something.

Ectrichodia crux belongs to the subfamily Ectrichodiinae, noted for their aposematic coloration – often red or yellow and black or metallic blue, and as specialist predators of Diplopoda (Heteropteran Systematics Lab @ UCR).  Species in this subfamily are most commonly found in leaf litter, hiding during the day under stones or amongst debris and leaving their shelters at night in search of millipedes (Scholtz and Holm 1985). They are ambush predators that slowly approach their prey before quickly grabbing the millipede and piercing the body with their proboscis, or “beak.”  Saliva containing paralytic toxins and cytolytic enzymes is injected into the body of the millipede to subdue the prey and initiate digestion of the body contents, which are then imbibed by the gregariously feeding assassin bugs.

Millipedes employ powerful chemical defenses – primarily benzoquinones and sometimes hydrogen cyanide gas as well, which are discharged from specialized glands along the millipede’s body – to protect themselves from predation.  Thus, specialized predation of millipedes is a niche that has been exploited by relatively few predators, and little is known about the mechanisms used for circumventing these defenses. The recently reported millipede specialist, Deltochilum valgum (order Coleoptera, family Scarabaeidae), has been observed killing its prey by violently decapitating and disarticulating it before feeding on the body contents (Larsen et al. 2009, summary here); however, the exact manner by which the beetle avoids or withstands the millipede’s chemical discharges remains unknown.  For ambush predators such as Ectrichodia crux and other ectrichodiines, a strategy similar to that described for another millipede specialist predator, larvae of the phengodid beetle, Phengodes laticollis (order Coleoptera, family Phengodidae), might be employed. This species subdues its millipede prey by piercing thinner regions of the millipede’s integument (e.g., intersegmental membranes on the ventral surface) with its hollow sickle-shaped mandibles and apparently injecting gastric fluids that abruptly paralyze the millipede, thereby preventing it from discharging its gland contents (Eisner et al. 1998).  These undischarged benzoquinones remain confined to the glands and are prevented from diffusing into the body cavity by the glands’ impervious cuticular lining, thus allowing the phengodid larva to safely imbibe the liquified systemic contents of the immobilized millipede.

REFERENCES:

Eisner, T., M. Eisner, A. B. Attygalle, M. Deyrup and J. Meinwald. 1998. Rendering the inedible edible: Circumvention of a millipede’s chemical defense by a predaceous beetle larva (Phengodidae).  Proceedings of the National Academy of Sciences USA 95(3):1108–1113.

Larsen, T. H., A. Lopera, A. Forsyth and F. Génier. 2009. From coprophagy to predation: a dung beetle that kills millipedes. Biology Letters DOI:10.1098/rsbl.2008.0654.

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

Reavell, P. E. 2000. The assassinbugs (Hemiptera: Reduviidae) of South Africa. http://oldwww.ru.ac.za/academic/departments/zooento/Martin/reduviidae.html#ectrichodiinae.

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

Copyright © Ted C. MacRae 2009

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Lions in South Africa

Joerie, Joerie, botter en brood,
as ek jou kry, slaat ek jou dood.

Doodlebugs, joerie, shunties, toritos—these are but a few of the many colloquial names given to amusing little creatures that many people know simply as antlions (or translation of such) (Swanson 1996).   Larvae of winged insects resembling (but unrelated to) dragonflies, they are best known for their habit of digging smooth-sided, cone-shaped pits in sandy soils and concealing themselves under the sand at the bottom.  There, they lay in wait for some small, unsuspecting creature—often an ant—to fall into the pit.  When that happens, the hidden antlion bursts forth, using its oversized, sickle-shaped mandibles to “flick” sand at the prey to keep it sliding towards the bottom of the hole.  Once it is within reach, the antlion grabs the prey using those same, deadly mandibles (how delightfully morbid!).  So otherworldly is their appearance and behavior that, in addition to inspiring children’s charms, they have served as an unmistakable model for the “Ceti eels” featured in Star Trek: The Wrath of Khan!1  Adults of this group, on the other hand, have inspired far less imagination in nomenclature and culture, to the point that even their common name “antlion lacewing” is merely a reference back to their unusual larvae.  Even the scientific name of the family—Myrmeleontidae—has failed to garner complete adherence, with “Myrmeleonidae” (who needs the “t”?) and “Myrmelionidae” (perhaps from English-speakers focused on the English spelling of “lion” rather than the Latin spelling of “leo”) still appearing in popular and even scientific literature.

1 Sadly (and ironically), actor Ricardo Montalban, who played the villain Khan Noonien Singh in that movie (reprising a character he played 15 years earlier during the debut season of the Star Trek television series), died just eight days ago at the age of 88. I must confess that I am a life-long Star Trek fan (though not a “Trekkie”), and “Wrath” was certainly among my favorite of the movies, due in large part to Montalban’s steely, venomous portrayal of Kahn. My favorite line occurs as Kahn is about to put a Ceti eel in Chekov’s ear, explaining how they wrap themselves around the victim’s cerebral cortex. He then says, “Later, as they [pauses deliciously] grow…”

myrmeleontidae-larval-pitI’ve seen antlion pits on several occasions (especially in recent years as I’ve spent more time in open sand habitats searching for my beloved tiger beetles).  However, the pit pictured here—encountered at Borakalalo National Park in South Africa’s North West Province, was the first I’d ever seen in which there was actually an ant inside the pit.  The ant was dead, presumably having already been sucked dry by the joerie. I didn’t know it at the time, but southern Africa is a major evolutionary center for antlion lacewings and some of their striking relatives such as spoonwinged and threadwinged lacewings (family Nemopteridae) and silky lacewings (family Psychopsidae) (Grimaldi & Engel 2005).  Relatively few of South Africa’s antlions, however, actually dig pits—a habit restricted to species in the genera Hagenomyia, Cueta, and the cosmopolitan Myrmeleon (Scholtz & Holm 1985).  Rather, the majority of species have free-living larvae that hide under objects or roam under deep sand from where they emerge to hunt other insects.

Palpares lentusThis adult antlion lacewing came to an ultraviolet light at our encampment on the Geelhoutbos farm near the Waterberg Range (Limpopo Province). Its tremendous size and distinctly patterned wings placed it in the tribe Palparini, of which the genus Palpares is the most diverse. These are the true giants of the family, with forewing lengths that can reach 75 mm (that’s 3 inches, folks!) and both wings bearing conspicuous patterns of black and yellow markings (the yellow doesn’t show well in this photograph due to illumination by the ultraviolet light).  The larvae, understandably, are also quite large, and have even been observed to capture ground resting grasshoppers (Capinera 2008).  I sent this photograph to Dr. Mervyn Mansell, an expert on African Myrmeleontidae, who kindly identified the individual as a female Palpares lentus, endemic to northern South Africa and Zimbabwe. When queried for more information regarding its biology, Dr. Mansell responded:

We know nothing about P. lentus, except for distribution records. Nothing is known about its larva or biology, although the larvae of all Palpares and related genera are obviously large, and live freely in sand well concealed and almost impossible to find.

Palpares lentus is one of 42 species of Palparini in southern Africa—half of all known species in the tribe.  Nearly two-thirds of them are endemic to “open” biomes in the dry western parts of the subregion (Mansell & Erasmus 2002).  This high level of endemism results from the occurrence of large tracts of sand and exposed soil that are conducive to the large sand-dwelling larvae.  Eastern parts of the subregion containing forest or thicket biomes are not as favored by antlion lacewings, and consequently the diversity of species in these areas is much lower.  Because of their great size, palparine adults are especially vulnerable to predation, with the result that they have evolved elaborately patterned wings to enhance their camouflage—apparently an adaptation to the dappled shade provided by the fine-leafed plants found in these biomes.  While many species in the tribe are diurnal, a few in the related genus Palparellus pulchellus and P. ulrike are known to be attracted to light, spending the day resting concealed amongst vegetation. The attraction of this individual to our ultraviolet light suggests Palpares lentus has similar habits.

Everything you want to know about antlions can be found at Mark Swanson’s excellent website, The Antlion Pit. For information specific to Africa, Mervyn Mansell has assembled a checklist of The Antlions (Neuroptera: Myrmeleontidae) of South Africa, and a nice summary of antlions in Kruger National Park by Dave Rushworth can be found at Destination Kruger Park. I thank Dr. Mansell for his identification of Palpares lentus.

REFERENCES:

Capinera, J. L. (ed.).  2008. Encyclopedia of Entomology, 2nd Edition. Springer, Dordrecht, The Netherlands. 4346 pp.

Grimaldi, D. and M. S. Engel. 2005. Evolution of the Insects. Cambridge University Press, New York, xv + 755 pp.

Mansell, M. W. and B. F. N. Erasmus. 2002. Southern African biomes and the evolution of Palparini (Insecta: Neuroptera: Myrmeleontidae). Acta Zoologica Academiae Scientiarum Hungaricae 48 (Suppl. 2):175–184.

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

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

Goin’ fishin’

For the past two days I’ve been in Sioux County, Nebraska – just east of Wyoming and just south of South Dakota. As I traveled up through the western panhandle to arrive at this spot, I was pleasantly surprised by the varied terrain – not at all the monotonously flat landscape that I expected. The landscape in this so-called Pine Ridge area is even more surprising – an impressive escarpment drops 1,400′ from the high shortgrass prairie down to an eery badlands below. The escarpment itself is forested with Ponderosa pine and is studded with numerous impressive buttes. The photos shown here were taken in Sowbelly Canyon – typical of the landscape along the escarpment – and in the badlands below Monroe Canyon a little further west.

Enough about pines and buttes – my business here is tiger beetles. I met up yesterday with tiger beetle aficionado Matt Brust, who recently took a position here at Chadron State College after finishing his Ph.D. in Lincoln. I’ve been corresponding with Matt for a bit now, and when I told him of my interest in doing a tiger beetle trip through western Nebraska, he was more than willing to show me around and hopefully help me find some of the more unusual species I was looking for. Of course, tops on the priority list was Cicindela nebraskana (prairie long-lipped tiger beetle). This beetle isn’t common anywhere within its range and just sneaks into the northwest corner of Nebraska, where the type locality is located. Until recently, the species was known from very few specimens in Nebraska. Matt did some intensive sampling a few years ago and located a few limited populations in the vicinity of the type locality. Yesterday, he took me to two of these localities, and we succeeded in finding one individual at the first and several at the second. It was at the type locality where I succeeded in getting this field photo. While admittedly harshly-sunlit, it is as far as I know the only field photograph of the species – all others that I’ve seen have been taken in terraria. I’ll fix it up a bit with Photoshop and re-post once I get back home. This species looks similar to the black morph of Cicindela purpurea audubonii, which co-occurs with C. nebraskana in Nebraska, but it lacks the bright white labrum and elytral markings of the former. Also, as I would learn during these past two days, it can be instantly recognized in the field by its shinier appearance and “stubbier” legs. A few days before my arrival, Matt succeeded in finding the species in the next county to the east, an eastern range extension of about 60 miles, and today I located the species at another new locality between the two. It is gratifying to have played a small role in increasing our knowledge about this unusual species.

My success with C. nebraskana has come despite uncooperative weather. A series of frontal systems has moved through the area since my arrival, resulting in several rain events and lots of cool, cloudy weather. Tiger beetles are sun-loving insects, and when it gets too cold or wet the adults dig in and don’t come out until the sun shines through or temps warm enough to trigger them to dig out. Matt had taken me to another locality – a sand embankment – where we might find the beautiful Cicindela lengi (blowout tiger beetle), but it rained prior to our arrival and we saw no activity. I tried finding adult burrows to dig them out, but the rain had obliterated any trace of the diggings, making their burrows impossible to find. We did, however, note an abundance of larval burrows. I went back to the spot today hoping to see some activity, but thick clouds and cool temps made that unlikely. This is when I decided to “go fishing.” Tiger beetle larval burrows are easily recognized by their perfect circular shape and clean “beveling” around the entrance (1st photo). Burrows of 3rd instars (the last larval instar in tiger beetles) are distinctly larger than those of 2nd instars (2nd photo), while those of 1st instars are smaller still (not shown). Larvae sit at the burrow entrance and ambush any suitable prey that comes too close. During cool, cloudy weather, however, they drop to the bottom of their burrow – up to a foot or more deep. A technique useful for extracting inactive larvae from their burrows is called fishing and involves inserting a thin grass stem down to the bottom of the burrow in an attempt to coax the larva into “taking the bait” and biting the end of the grass stem (3rd photo). The grass stem is then pulled up rapidly – much like setting the hook when fishing – in an attempt to pull the larva out of its burrow before it has a chance to let go of the stem. It can take a few tries, but with practice one can more often than not succeed at removing the grotesquely odd, yet beautiful larva (4th photo). Note the huge, heavily sclerotized head with upward facing jaws. The hump in the middle of the back is armed with forward-curved spines that helps the larva avoid being pulled out of the burrow by struggling prey (but they’re not so effective against obsessive cicindelophiles!). As I managed to “fish” larvae I placed them in a plastic container with their native soil. In the 5th photo, four larvae have already begun digging new burrows, and one more 3rd instar (L) along with a 2nd instar (R) has just been placed in the container. I’ll bring this container back with me and continue to feed the larvae live insects in the hopes of rearing them to adulthood. I cannot say with certainty that the larvae I collected represent C. lengi – other species that could potentially occur at this site include C. scutellaris (festive tiger beetle) and C. limbata (sandy tiger beetle). However, the locality is known for the abundant occurrence there of C. lengi, so I’m hopeful that that is what I’ve collected – we’ll know in a few weeks. In the meantime, I’ll have additional opportunities to look for this species, along with C. limbata, as I pass through the Sand Hills region later this week.

Tomorrow morning I head to the Black Hills in South Dakota, where I hope to find not only Cicindela longilabris laurentii (Boreal long-lipped tiger beetle) in the high pine forests, but also intergrades between this species and the closely related C. nebraskana in the more open habitats of the middle latitudes. Look for an update in a couple days or so.