February 7, 2009 12 Comments
In the 19th and early 20th centuries, some of the America’s greatest entomologists were coleopterists. Army surgeons John L. LeConte and his protégé George W. Horn, California’s Henry C. Fall, Col. Thomas L. Casey (much maligned for his mihi itch¹ affliction, although in recent years regaining due respect for his insight on generic relationships), and “the Professor” Josef N. Knull, just to name a few. What did these fine men have in common? They studied beetles – not just tiger beetles or jewel beetles, but the entire order! The world was much smaller then, and new information was generated at a much more leisurely pace. Today such an approach is impossible. With 300,000 described species in the order (conservatively) and growing, today’s students of Coleoptera must narrow their focus in one way or another – either by concentrating on one family or ecological guild, or by restricting their studies to a small geographic region. I’ve tried, more or less successfully, to follow suite – jewel beetles are my primary focus, and I restrict my work with the ecologically similar longhorned beetles only to North American species. Well, and I’m also working on tiger beetles, but only in Missouri… although I have begun taking fall tiger beetle trips to neighboring states. Hmm, on second thought, I guess I haven’t been that successful at focusing (sigh! – and a likely explanation for my perpetual backlog of specimens unprocessed and papers unwritten).
¹In taxonomy, a term usually cast towards those who have a combination of disregard for quality over quantity when describing new taxa and a demonstrably high ego (Evenhuis 2008).
Whatever focus I do manage, it all goes out the window when I have the chance to collect in another country – especially someplace as exotic as Africa. This is not a huge problem, as I can at least stay pretty much focused on just beetles. Moths and butterflies are pretty, but it just takes too much effort to keep each specimen in good shape. Bees and wasps also capture my interest, but I never know for sure whether I’ll get stung, and the extra precautions required to avoid such possibility are enough to make me pass on them. Orthopterans don’t generally excite me unless they’re big and gaudy – in which case just one or two for the collection is fine. And flies? Well, they’re flies! About the only non-coleopterans that regularly distract me are treehoppers – running into a mess of them, with their bizarre, fantastical shapes will always stop me in my tracks. Fortunately, they’re not so abundant that they are constantly grabbing my attention.
Beetles, though – that’s a different story. While I can resist the temptation to collect many of the groups outside of my sphere of interest, there are others that are consistently too tempting for me to pass up. One of these is the Tenebrionidae, or darkling beetles. With some 20,000 described species worldwide, it is among the most speciose of beetle families (larger than my beloved Buprestidae), and this diversity combines with difficult taxonomy to make them truly challenging for even the most serious students of the family. For hacks like me, they’re impossible. Moreover, they’re not even especialy pretty – usually just black. Why do I collect them? Mostly because of their (in many cases) large size, comically awkward shuffling gait, and often exaggerated surface sculpturing. Especialy diverse in more xeric habitats, I’ve collected quite a few in my frequent trips through the southwestern U.S. and even managed to get many of them identified by tenebrionid icon Charles A. Triplehorn. Southern Africa is a true center of diversity for this group, with some 3,500 species recorded from the area – nearly 20% of the global diversity! A number of particularly large species that go by the common name “tok-tokkies” make their homes in the dry Namib desert and surrounding bushveld. Along with dungers and chafers and tyrant ground beetles, tok-tokkies would prove to be one more distraction in my nevertheless successful quest for African jewel beetles.
“Tok-tokkie” refers not to a particular genus or tribe of tenebrionids, but rather a number of flightless species that have developed a unique “tapping” method of communication between males and females. The name “tok-tokkie” is onomatopoeic, referring to the sound these beetles make when they tap their abdomen on the ground. In the same way that fireflies have species-specific patterns of flashes, different species of tok-tokkies tap with differing frequencies. The beetle makes the noise by raising its abdomen and then bringing it down on the surface of the ground several times in quick succession. Males initiate the tapping and await a response from a receptive female. Signals are exchanged back and forth until, eventually, the two locate each other and mate. Females lay eggs in shallow excavations in the dry, sandy soil, and the larvae that hatch feed within the soil on the roots of small plants. The dry Namib Desert has some of the most astounding species of tok-tokkies. Some – called “fog tok-tokkies” – have developed specially modified grooves to trap moisture from fog banks rolling onto the Atlantic coast. Others drink by doing a “head-stand” to allow condensed dew to trickle down to their mouths. Heat avoidance is another challenge in the Namib. Some species extrude dots of white wax from small pores on their elytra in response to increasing sunlight intensity, eventually appearing white-spotted or striped. The wax reflects the sun’s rays and helps keep the beetle cool. Other species beats the heat by running – in fact, the fastest running beetle in the world is one of the Namib tok-tokkies (and not, as I would have suspected, a tiger beetle). Unlike its mostly clumsy brethren around the rest of the world, this beetle blasts across the scorching sand at lighting speeds. A related species boasts the longest relative leg length of any beetle in the world.
I knew none of this in 1999 when I was in South Africa’s Northern (now Limpopo) Province, and while the tok-tokkies we encountered in the bushveld habitat below the Waterberg Range were not quite as marvelous as those of the nearby Namib Desert, they were still irresistible to this indefatigable beetle collector. Not knowing their names, we came up with our own names for them based on their appearance. Psammodes hirtipes was “wrinkle butt” due to the numerous prominent tubercles at the sides and rear of its otherwise smooth elytra. Psammodes virago, was “helmet beetle” because of its smoothly domed “army helmet” shape. Our designation of “armoured tank beetle” for Anomalipus elephas (photo credit) was amazingly close to its actual common name of “large armoured darkling beetle” (Picker et al. (2002), as was “white legs” for Dichtha incantatoris (photo credit), which Picker et al. (2002) call the “white-legged tok-tokkie”. In all, I collected some dozen species of tenebrionids during my stay at Geelhoutbos farm. Most of the smaller ones are still unidentified, but hopefully someday they will prove useful to some tenebrionid specialist.
The online magazine Travel Africa offers an informative article about the Namib tok-tokkies and this humerous video from National Geographic:
Evenhuis, N. L. 2008. The “Mihi itch”—a brief history. Zootaxa, 1890:59-68.
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 2009