Limnocentropodidae: The Tethered Casemakers.

Limnocentropodidae is a small family of case making caddisflies distributed throughout the East Palearctic, from Nepal to Japan, to India and Indonesia in the South. The family consists of a single genus, Limnocentropus, containing 15 described species (Trichoptera World Checklist, 2012). Larvae are filter feeders in streams and rivers (sometimes torrential currents), facing head and legs first into the current much like the common Nearctic genus Brachycentrus (Brachycentridae), but it is there that any similarities to other casemaking caddisfly families end.

A Limnocentropus insolitus larva, from Haiya, Kyoto Prefecture, Japan. The photographer calls it a "kita gami", the Japanese name for the group. (© 2011 hir**amiyam*)

Both the larvae and adults are aberrant among other casemaking caddisfly families in their morphology and the odd architecture of the cases. As can be seen partially in the photo above, the case is a tapered tube of rock and leaf fragments, tethered to the substrate via a tough, silken stalk nearly as long as the case, and coated in tiny silk denticles. These predatory larvae extend their stout, hairy legs into the current like a net, snagging drifting insect larvae and other aquatic invertebrates. When it comes time to pupate, the larvae narrow the posterior end of the case, shorten the stalk, and build a wide collar around the anterior opening, possibly to help funnel water through the case. Some species will form their pupal houses in long chain like aggregations, with the stalks attached to the preceding cases (Wiggins 2004). Adult limnocentropodids are unique in retaining hardened mandibles; most caddisflies have only a sponge-like haustellum (Latin for "little suck") much like that of a house fly. (Kjer 2010).

A Limnocentropus himalayanus male. Despite being present, the mandibles are quite small and nearly undetectable in this photo. (Kjer 2006, Public Domain)

Because these stalk-casemakers are so weird, trichopterologists have had a hard time classifying this family. Glen Wiggins and Henry Frania (1997) placed Limnocentropodidae as a sister family to the rest of the case making caddisflies based in not possessing characters placing them in either the Brevitentoria (Herbert Ross's "long-horned-caddis-like" group) or the Plenitentoria ("northern-casemaker-like" group). More recent work using molecular characters (Kjer et al. 2002) and combined molecular and morphological characters (Holzenthal et al. 2007) supports placement within Brevitentoria, but any deeper classification has been unstable (Kjer 2010).

References

Frania, H. E., and G. B. Wiggins. 1997. Analysis of morphological and behavioural evidence for the phylogeny and higher classification of Trichoptera (Insecta). Life Sciences Contributions, Royal Ontario Museum, 160, 1–67.

Holzenthal, R. W., R. J. Blahnik, K. M. Kjer, and A. L. Prather. 2007. An update on the phylogeny of Caddisflies (Trichoptera). Proceedings of the XIIth International Symposium on Trichoptera. Bueno-Soria, R. Barba-Alvearz and B. Armitage (Eds). pp. 143-153. The Caddis Press.

Kjer, K. M. 2010. Limnocentropodidae. Limnocentropus. Version 20 July 2010 (under construction). http://tolweb.org/Limnocentropus/14593/2010.07.20 in The Tree of Life Web Project, http://tolweb.org/ [Accessed 17 February 2012].

Kjer, K. M., R. J. Blahnik, and R. W. Holzenthal. 2002. Phylogeny of Caddisflies (Insecta, Trichoptera), Zoologica Scripta 31(1) :83-91.

Morse, J. C. (ed.) 2012. Trichoptera World Checklist http://entweb.clemson.edu/database/trichopt/index.htm [Accessed 17 February 2012]

Wiggins, G. B. 2004. Caddisflies: The Underwater Architects. University of Toronto Press, Toronto, ON. [ed: includes detailed drawings of larval and case morphology]