Sunday, February 26, 2012

The fly with the feathery antennae.

In 2009, my mentor was part of an ecosystem survey project at Lago Copa, a recently created national park in Chile. He was using Townes traps to collect adult caddisflies, but he also kept representatives from other groups, including Diptera. When he returned I volunteered to sort out the caddisflies (these were alcohol-preserved samples he hand picked in the field), and I also sorted out any fungus gnats I found. The gestalt for many fungus gnats is easy enough to pick them out around other flies, even without magnification. They tend to have long antennae, long coxae and legs, multiple tibial spurs, a thin, curving abdomen that widens towards the tip, and often have patterned wings. They also tend to be laterally flattened, which sets them off from the boxy muscoid flies. In particular, I was looking for members of the family Keroplatidae, some of which have stout, flattened antennae as well as the above characters. If I had to describe the over all shape in simple terms, they look like two arches joined by three pillars, with wings outstretched behind.

Imagine my surprise when I found this critter among the mix.

The mystery fly, semi-left habitus. CHILE: PROVINCIA AYSEN: Municipalidad Cisnes, Parque Nacional Lago Copa, S. side of E. Lago Copa, unnamed 1st order stream, from cascade 200 m E. of Cliffs Lodge, S44.89155, W072.62070, 15-18.xii.2009.

If this was a fungus gnat, it was the strangest individual I had ever seen. First of all, the antennae are pectinate (feather-like), and there are few Diptera which have this character. This wouldn't eliminate Sciaroidea from the search, since there are genera in Ditomyiidae, Mycetophilidae, and Keroplatidae with species bearing pectinate antennae (Matile 1981). But then there are the other unusual characters.

The hindlegs are like nothing I had seen before. The tibiae are bowed and pressed forward in a grove against the femurs, so the tarsi lay close to the coxae. They resembled those of chalcid parasitoid wasps, which use those strong hind legs to capture prey for their young. The abdomen is short and conic. And the wings confuse the rest.

The wing veination looks as if it could have come from a fungus gnat, but the thick apical stigma and just how strong the veins are, how dark and heavy, reminds me more of a wasp wing. The halters mean it is obviously a true fly, but it looks like someone has glued on parts from other insect orders. I sent some pictures to Sciaroidea experts but the identity of this chimera continued to be a mystery.

I finally sent the above photos to Dalton de Souza Amorim, a South American fly expert, and he replied with a diagnosis he was nearly 100% sure of. But this was not a fungus gnat. It wasn't even in the Sciaroidea superfamily. This was a Canthyloscelidae.

Wing of male Exiliscelis californiensis from the Synneuridae chapter of Manual of Nearctic Diptera. (Via DrawWing) If I didn't know better, I would say this came from a keroplatid.
The family Canthyloscelidae is a small family of flies in the "lower" Diptera, with ~15 extant species in 4 genera, found native in all faunal regions except the East Palearctic and Afrotropics. There is disagreement as to whether it should be placed with the Bibiomorpha or Psychodomorpha; larval structures suggest the latter (Amorim 2008) while adult characters alone suggest the former. Canthyloscelidae used to be split into two or more families, the Synneuridae and Canthyloscelidae (sometimes previously combined under Hyperoscelidae (Hutson 1977)), but these were joined by the time of Haenii's canthyloscelid chapter in Contributions to a Manual of Palearctic Diptera (1997).

This particular species is Canthyloscelis pectinata, the only species in this family with the males bearing strongly pectinate antennae. It has been recorded from Argentina and Chile in very low numbers (Hutson 1977), which means this may be one of less than 20 specimens ever collected, a rare find (Amorim pers. com.).

Exiscelis californiensis gathering on Potentilla flowers, Lowder Mountain, Oregon. (© 2011 Jake Hurlbert)

In North America, there are two species of Canthyloscelidae in two genera, Synneuron decepiens and Exiscelis californiensis. S. decepiens is found at Northern latitudes across the continent, while E. californiensis is only found on the Northwest Coast. Both are found in "ancient forests" (Triplehorn and Johnson 2004). Very little is known about their biology; larvae live in decaying wood "permeated by [fungal] mycelia" (Peterson and Cook 1981), and this family's close relationship with Scatopsidae suggests they feed on the fungi and microorganisms associated with such habitats.

In all, it was a nice little treasure hunt. I think taking time to jump outside my comfort zone and identify something so strange to my experience is an excellent exercise. It improves my skill as a taxonomist and teaches me about groups beyond my research. But most of all, identifying something weird is /fun/. Finding something strange and new, even if it's just new to you, is one of the greatest pleasures of natural history research.

Haenni, J.-P. 1997. Family Canthyloscelidae. In Papp L. & Darvas B. (eds): Contributions to a Manual of Palaearctic Diptera. Nematocera and Lower Brachycera.. Vol. 2. Budapest: Science Herald. pp. 273–279.

Hutson, A. M. 1977. A revision of the families Synneuridae and Canthyloscelidae (Diptera). Bulletin of the British Museum (Natural History) Entomology 35(3):67-100.

Johnson, N. F., and C. A. Triplehorn. 2004. Borror and Delong's Introduction to the Study of Insects, 7th ed. Brooks Cole, St. Paul, MN.

Matile, L. 1981. A new Austrailian genus of Keroplatidae with pectinate antennae (Diptera: Mycetophiloidea). Journal of the Austrailian Entomological Society 20: 207-212.

Peterson, B. V., and E. F. Cook. 1981. Chapter 21. Synneuridae. Manual of Nearctic Diptera 1: 321-324.

Friday, February 17, 2012

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).


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). in The Tree of Life Web Project, [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 [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]

Monday, February 6, 2012

Entomological Museums: Little progress in 60 years.

At the 1949 meeting of the Pacific Coast Entomological Society, retiring president Edward S. Ross gave an address on the role of entomological museums. He outlined six major functions which can be applied to natural history collections in general.

1. To preserve specimens: "In thus preserving and making available for use the specimens upon which the literature is is based the museum performs one of its most important functions; namely, that of being a place where collections can be received curated, and preserved for future reference."

2. To serve as gathering point for newly collected and unstudied specimens: "When a museum fails to gather new material it is as dead and as unproductive as a machine without fuel."

3. To provide facilities and loan material for specialists:
All museums, of course, attempt to have table space and equipment for visiting scientists...Obviously, however, it is impossible for a specialist personally to visit each museum in the course of a given taxonomic project...Curators, because of pressure of other work, or a fewar of losing specimens, unfortunately are not always eager to fill loan requests. They should realize, however, that it is one of their primary duties to honor any loan request made by a worker in good standing, or who is properly recommended. Unstudied specimens lying idle in museums at a time when revisionary work is being done might just as well be back in the field if they are not utilized during such fleeting periods of activity.
4. To specialize (to some extent) in a particular group or region: "The resultant development of outstanding collections in a taxonomic group is a desirable and an essential step towards making real published conclusions."

5. To provide representative sets of specimens for major groups around the world: "In many orders higher categories have been very incompletely correlated from a world standpoint. There is a need for first hand examination, not a mere literature knowledge, of the type species upon which these categories are based."

6. To educate the public: "Very often [the museum] is the only place where youth, the post-university-age amateur, and the professional entomologist can find the means for pursuing his work...Avocational entomology can add to the fullness of many a life and this fact alone could well justify the place of museums in our society."

The major problem with meeting these functions, he said, "is financial support of the activity is more in proportion to the size of the organisms, than to the size of the job." Charismatic megafauna such as birds and mammals often receive greater funding, despite smaller amounts of taxonomic work needed in those groups. And in the eyes of the public, these tasks lack the shiny, new appeal of other sciences based in high technology. Shortages in staffing, space and organizing materials are due to museum work being "like that of a library...very unspectacular."

To Dr. Ross, the single most important progressive change needed was freer loaning of type specimens between institutions, with a central filing system containing information on the types for all names of insects worldwide. The most controversial aspect of his proposal was a central type depository, perhaps at the Smithsonian, where all holotype specimens collected in the United States would be located.

I am sure the immediate reaction of many curators to this proposal will be one of horror, but most of this horror I believe would be based on unscientific selfish reasons. it is not the purpose of types to make an institutional or private collection valuable or indispensable. Admittedly it would mean that some museums would give up more than others. As matters stand, however, no institution is self-sufficient in regard to types and all stand to gain in the long run. What is really important is that our ponderous science would advance more rapidly with unwavering, steady steps. [emphasis his]
It is clear after 60 years that this dream is far from being realized. The problems of staff and funding shortages are the same today as they were then, if not worse. And central type depositories aside, there is still no central database of names and types for insects. This is in spite of the ubiquity of Internet, and many independent attempts by taxonomists in their groups of specialization. Many museums are digitizing their collections, but these catalogs are institutional and seldom connected to each other. Despite technological progress, natural history collections have a long way to go before name and type information is completely available. The problems of today are the same as then.

Thanks to Doug Yanega of the Entomological Collections Network listserv for the tip-up to this article.

Ross, E. 1950. The Role of the Entomological Museum. Pan-Pacific Entomologist 26: 1-10.