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).
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 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)!
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