large aquatic lep cocoons in Brazil

[Doug Yanega]

Just had some students show me some remarkable cocoons they found on the
upper surfaces of rocks in some streams in the "campo rupestre" around here
(about 1300m elev.). The largest were around 25mm, oval, with a flattened
outer silk covering with perforations around the edge, an inner elongated
cocoon, and the pupal exuviae looked to be about 12-15mm long. I'm not
aware of any leps that make cocoons on rocks underwater (the aquatic
cocoons I know of are all made of plant material), though a professor here
has suggested Cosmopterygidae, but I know of no aquatic Cosmos - just
Arctiids and Pyralids. But there are no hairs like might be in an Arctiid
cocoon, and these would be very large for Pyralids. The presence of a few
scales in the exuviae confirms that they are leps, not caddisflies,
incidentally. Does this ring any bells for anyone out there?

Cheers,

Doug Yanega    Depto. de Biologia Geral, Instituto de Ciencias Biologicas,
Univ. Fed. de Minas Gerais, Cx.P. 486, 30.161-970 Belo Horizonte, MG   BRAZIL
phone: 031-449-2579, fax: 031-441-5481  (from U.S., prefix 011-55)
                  http://www.icb.ufmg.br/~dyanega/
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