Red-eyed poop!

I was looking at some of my older files and ran across these photographs taken in early 2011 in Campinas (São Paulo state), Brazil. They’re not my best photos from a compositional and technical perspective, as I was still on the steep part of the learning curve with the Canon MP-E 65mm macro lens. This lens is no doubt powerful and allows amazingly close-up photographs, but it is rather a beast to learn in the field, especially hand-held. I could quibble endlessly about missed focus and suboptimal composition with these shots, and that is probably why they never made it to the front of the line for being posted. Nevertheless, they still depict some interesting natural history by one of nature’s most famous natural history poster children—the treehoppers (order Hemiptera; family Membracidae).

An adult next to a cast nymphal exuvia.

Bolbonota sp. (Hemiptera: Membracidae), upper right | Campinas, São Paulo, Brazil. Note cast exuvia.

The treehoppers shown in these photos were found on a low shrub in a municipal park and are all that I could manage before my clumsy, unpracticed molestations caused the few adults and nymphs present in the aggregation to disperse. The dark coloration of the adult and its globular form, corrugated pronotal surface, and lack of any horns identify the species as a member of the genus Bolbonota in the New World tribe Membracini (another similar genus, Bolbonotoides, occurs as a single species in Mexico). Species identification, however, is much more difficult, as there are at least a dozen species recorded from Brazil and perhaps many more awaiting description. We have a similar though slightly more elongate species here in eastern North America, Tylopelta americana. I don’t know if this is a specific character or not, but I don’t recall seeing any members of this genus with smoldering red eyes—it gives them an almost devilish appearance, especially the blackish adults (see last photo)!

Bolbonota sp. late-instar nymphs clustered together.

Bolbonota and similar genera are often cited by evolutionists as examples of insects that mimic seeds. I can see such a resemblance if I force myself, but honestly I don’t really buy it. To me they seem to bear an uncanny resemblance to the chlamisine leaf beetles which are thought to mimic caterpillar frass. As with the beetles they resemble, frass-mimicry seems to make much more sense than seed-mimicry, especially given their preference for positioning themselves along the stems of the plants on which they feed (when was the last time you saw seeds of a plant randomly distributed along its stems?). Another thought I’ve had is that this is not an example of mimicry at all, but merely an accidental consequence of the heavy, corrugated body form they have adopted, which likely also affords them a reasonable amount of protection from predation. Confounding both of these theories, however, are the radically different appearance and form of the adults versus the nymphs, and indeed even between the different nymphal instars (see early- and late-instar nymphs in photo below). The later instars seem perfectly colored for mimicking unopened leaf buds, but why they would start out dark in early instars before turning mottled/streaked-white as they mature, only to revert back to dark when reaching adulthood, is a mystery to me. If my thoughts are anywhere close to the truth, it would be a remarkable case of different life stages mimicking the products of two different taxonomic kingdoms (plant parts as nymphs, animal poop as adults)!

Bolbonota sp. nymphs tended by Camponotus sp. | Campinas, São Paulo, Brazil.

An ant (presumably Camponotus sp.) tends a first-instar nymph alongside a later instar.

Of course, if either/both of these lines of defense fail then there are the ant associates that often protect treehoppers and other sap-sucking, aggregating insect species in exchange for the sweet, sugary honeydew that such insects exude as a result of their sap-feeding habits. I presume this ant belongs to the genus Camponotus, perhaps C. rufipes or C. crassus which are both commonly encountered treehopper associates in southern Brazil. I have written previously about ant-treehopper mutualism in the stunningly-marked nymphs of another treehopper, Guayaquila xiphias, and its ant-associate C. crassus in Brazil Bugs #15 – Formiga-membracídeos mutualismo (a post that has become one of this blog’s most popular all-time). Maybe this post will never match that one in popularity, but I do find the third photo shown here remarkable in that is shows no less than five elements of this treehopper’s natural history (early-instar nymph, late-instar nymph, cast nymphal exuvia, partial adult, and an ant-associate) within a single frame (shot by a person still on the steep portion of the MP-E 65mm learning curve!).

Copyright © Ted C. MacRae 2013

Brazil Bugs #15 – Formiga-membracídeos mutualismo

Of the several insect groups that I most wanted to see and photograph during my trip to Brazil a few weeks ago, treehoppers were near the top of the list.  To say that treehoppers are diverse in the Neotropics is certainly an understatement – South America boasts an extraordinary number of bizarre and beautiful forms that still, to this day, leave evolutionary biologists scratching their heads.  The development of this amazing diversity is a relatively recent phenomenon (thinking geological scale here), as there are no known membracid fossils prior to Oligo-Miocene Dominican and Mexican amber – well after the early Cretaceous breakup of Gondwanaland split the globe into the “Old” and “New” Worlds.  With its origins apparently in South America, numerous groups continued to spring forth – each with more ridiculous pronotal modifications than the last and giving rise to the dazzling diversity of forms we see today.  Even North America got in the evolutionary act, benefiting from northern dispersal from South America’s richly developing fauna via temporary land bridges or island stepping stones that have existed at various times during the current era and giving rise to the almost exclusively Nearctic tribe Smiliini (whose species are largely associated with the continent’s eastern hardwood forests).  Only the subfamily Centrotinae, with its relatively unadorned pronotum, managed to successfully disperse to the Old World, where it remains the sole representative taxon in that hemisphere.  With a few notable exceptions, treehoppers have virtually no economic importance whatsoever, yet they enjoy relatively active study by taxonomists, evolutionists, and ecologists alike – due almost completely to the bizarreness of their forms and unique mutualistic/subsocial behaviors.

I did manage to find a few species of treehoppers during the trip (a very primitive species being featured in Answer to ID Challenge #4 – Aetalion reticulatum), and of those that I did find the nymphs in this ant-tended aggregation on a small tree in the rural outskirts of Campinas (São Paulo State) were perhaps the most striking in coloration and form.  Most were jet black, although a few exhibited fair amounts of reddish coloration, and all exhibited sharply defined white bands of wax and long erect processes on the pronotum, mesonotum, and abdomen.  I’ve seen a fair number of treehopper nymphs, but I did not recognize these as something I had seen before, and given the incomplete state of immature taxomony I feared an identification might not be possible.  Still (and I know this is probably beginning to sound like a broken record), I gave it the old college try.

I usually like to start simple and get more creative if the results aren’t satisfactory, so I went to my old friend Flickr and simply typed “Membracidae” as my search term.  Predictably, pages and pages of results appeared, and I began scanning through them to see if any contained nymphs at all resembling what I had.  After just a few pages, I encountered this photo with very similar-looking nymphs, and although no identification beyond family was indicated for the photo, I recognized the lone adult sitting with the nymphs as a member of the tribe Aconophorini – a diverse group distinguished from other treehoppers by their long, forward-projecting pronotal horn.  Luck was with me, because I happen to have a copy of the relatively recent revision of this tribe by Dietrich and Deitz (1991).  Scanning through the work, I learned that the tribe is comprised of 51 species assigned to three genera: Guayaquila (22 spp.), Calloconophora (16 spp.), and Aconophora (13 spp.).  The latter two genera can immediately be dismissed, as ant-interactions have not been recorded for any of the species in those two genera – clearly the individuals that I photographed were being tended by ants.  Further, the long, laterally directed apical processes of the pronotal horn, two pairs of abdominal spines, and other features also agree with the characters given for nymphs of the genus Guayaquila.  In looking at the species included in the genus, a drawing of a nymph that looked strikingly similar to mine was found in the species treatment for G. gracilicornis.  While that species is recorded only from Central America and northern South America, it was noted that nymphs of this species closely resemble those of the much more widely distributed G. xiphias, differing by their generally paler coloration.  My individuals are anything but pale, and reading through the description of the late-instar nymph of the latter species found every character in agreement.  A quick search of the species in Google Images was all that was needed to confirm the ID (at least to my satisfaction). 

In a study of aggregations of G. xiphias on the shrub Didymopanax vinosum (Araliaceae) in southeastern Brazil, Del-Claro and Oliveira (1999) found an astounding 21 species of associated ant species – a far greater diversity than that reported for any other ant-treehopper system.  The most frequently encountered ant species were Ectatomma edentatum, Camponotus rufipes, C. crassus, and C. renggeri, and after perusing the images of these four species at AntWeb I’m inclined to believe that the ants in these photos represent Camponotus crassus (although I am less confident of this ID than the treehoppers – corrections welcome!).  The authors noted turnover of ant species throughout the day in a significant portion of the treehopper aggregations that they observed, which they suggest probably reflects distinct humidity and temperature tolerances among the different ant species and that might serve to reduce interspecific competition among ants at treehopper aggregations.  Since treehopper predation and parasitism in the absence of ant mutualists can be severe, the development of multispecies associations by G. xiphias results in nearly “round-the-clock” protection that can greatly enhance their survival.

Update 3/3/11, 9:45 a.m.:  My thanks to Chris Dietrich at the Illinois Natural History Survey, who provided me in an email exchange some clarifying comments on the origins and subsequent dispersal of the family.  The first paragraph has been slightly modified to reflect those comments.

REFERENCES:

Del-Claro, K. and P. S. Oliveira. 1999. Ant-Homoptera interactions in a Neotropicai savanna: The honeydew-producing treehopper, Guayaquila xiphias (Membracidae), and its associated ant fauna on Didymopanax vinosum (Araliaceae). Biotropica 31(1):135–144.

Dietrich, C. H. and L. L. Deitz.  1991.  Revision of the Neotropical treehopper tribe Aconophorini (Homoptera: Membracidae).  North Carolina Agricultural Research Service Technical Bulletin 293, 134 pp.

Copyright © Ted C. MacRae 2011