The last day of my vacation week in Corrientes, Argentina got off to a bad start—heavy rain moved in during the morning, and I feared my last chance at looking for insects was about to be washed away. The weather radar, however, showed a curious, abrupt line between rain/no rain across the river in Chaco Province. At noon I decided it was do or die and played a hunch that one of my favorite spots ~50 km west might have been spared the downpour, and if not at least I tried. Yet another example of how it usually pays to play your hunches—while the skies were gray and the ground and foliage a little damp, there was plenty of insect activity afield (and perhaps even enhanced by the first significant moisture in almost two months).

Tetanorhynchus poss. n. sp. | Chaco Province, Argentina

No sooner than had I walked 20 feet from the car did I see an enormous stick insect in a low, spreading acacia tree. I don’t know why I saw it, as it’s camouflage was quite effective, but after so many years of doing this I think I’ve just developed an eye for seeing things often easily missed. This, of course, is not your normal, run-of-the-mill (at least to North Americans) walkingstick (order Phasmida), but rather a member of the curious and exclusively Neotropical grasshopper family Proscopiidae, referred to in English as “jumping sticks” and in Spanish as “bicho palito” (stick bug). I recognized the family instantly, as I had already seen one of these a number of years ago in Uruguay (though not so large as this one), and of course Alex Wild featured what has become one of his most famous photos of a species from Ecuador in one of his Monday Night Mystery posts.

The super elongate fastigium suggests this may be a new species.

Gleefully I set about taking photos, focusing almost exclusively on the head. One thing that immediately struck me was the super-elongate fastigium (frontal projection)—many proscopiids lack this elongate fastigium, and I had not recalled seeing any example as long as the one on this individual. When I saw the super-closeup I had taken of the eyes and antennal bases from the ventral view, I knew I had my own Super Crop Challenge. Of course, it was not until after I posted the challenge that I realized identifying this insect below the family level was more of a challenge than I had anticipated. How could I award points for genus when I wasn’t even sure of this myself? Eventually I enlisted the help of Alba Bentos-Pereira at São Paulo University—he and his doctoral student are perhaps the only two people in the world that are working on this family. I had suggested, based on its location in Chaco Province and consulting Orthoptera Species File Online, that it must be either Tetanorhynchus calamus or Cephalocoema daguerrei—both in the tribe Tetanorhynchini (Bentos-Pereira 2003). Alba kindly responded that it could be the former, it most definitely is not the latter, and perhaps most likely is that it represents an undescribed species (proscopiid taxonomy is still far from complete). He indicated that the presence of ventral spines on the metatibia would confirm membership in the tribe Tetanorhynchini (they are present), and provided several measurements from the male holotype of T. calamus that I could use to compare with my specimen. Although the absolute measurements might (and probably would) differ, their relative proportions should be the same as the type. Here are the results (measurements in mm):

As can be seen, most of the measurements are consistently 1.2–1.4X that of the male type. The head, however, is proportionately longer (1.7X), primarily due to the much longer fastigium (2.0X). Is this difference significant, at least enough to consider it a different species? I am currently awaiting Alba’s opinion on that.

Like all proscopiids, the form of the face seems to be''smiling'.'

While only two species of Proscopiidae are described from Chaco Province, there are eleven species known from northeastern Argentina (which includes the provinces of Buenos Aires, Chaco, Córdoba, Corrientes, Entre Rios, Formosa, Missiones and Santa Fe)—these are shown in the following list with hyperlinks to their respective pages at Orthoptera Species File Online, along with notes on type localities for each (or synonyms) and the length of the fastigium relative to the body:  

• Family Proscopiidae
  • Bolidorhynchus insignis (Hebard, 1931) – Formosa (fastigium short)
• Subfamily Xeniinae
  • Altograciosa mirabilis Liana, 1980 – Córdoba (fastigium short)
• Subfamily Proscopiinae
  • Anchocoema illudens Mello-Leitão, 1939 – Córdoba (no photo)
  • Carphoproscopia lancea (Burmeister, 1880) – Entre Rios, Córdoba, Mendoza (fastigium highly elongate)
• Tribe Tetanorhynchini
  • Cephalocoema bonariensis Piza, 1981 – Buenos Aires (no photo)
  • Cephalocoema curtirostris Mello-Leitão, 1939 – Córdoba (fastigium short)
  • Cephalocoema daguerrei Mello-Leitão, 1939 – Chaco (no photo, known only from the male holotype)
  • Mariascopia elegans Bentos-Pereira, 2003 – Córdoba (fastigium short)
  • Orienscopia angustirostris (Brunner von Wattenwyl, 1890) – Entre Rios (fastigium short)
  • Orienscopia costulata (Burmeister, 1880) – Córdoba (fastigium short)
  • Tetanorhynchus calamus (Burmeister, 1880) – Chaco (fastigium moderately elongate)

Okay, in the title I indicated this was “My longest post ever!” Here’s why:

Congratulations to Sam Heads, whose work as a practicing orthopteran taxonomist and contributor to Orthoptera Species File Online set him up for the win with 17 points. Brady Richard takes 2nd place with 14 pts, while Chris Grinter and Dennis Haines share the final podium spot with 12 pts each. Congratulations to these folks, who jump out of the gate early in BitB Challenge Session #6.

REFERENCE:

Bentos-Pereira, A. 2003. The Tribe Tetanorhynchini, nov. (Orthoptera, Caelifera, Proscopiidae). Journal of Orthoptera Research 12(2):159–171.

Copyright © Ted C. MacRae 2012