20 



NATURAL HISTORY. 



case is formed as above, of coarse sand-grains and small stones, but in addition to these the larva 

 adds larger angular stones along the sides, which give the case a very broad and depressed 

 appearance. Brachycsntrus nubilus, a British species, makes a quadrangular case of vegetable 

 materials. The most remarkable cases formed by larvae of this group are those of the genus 

 llelicopsyche, several species of which occur in South Europe, and one is recorded from North 

 America, while some analogous forms are described by Dr. Fritz Miiller as occurring in Brazil. 

 The cases of the larvae are composed of sand-grains and small stones embedded in the silken 

 material forming the actual case ; but, unlike any of the cases already described, they are of a spiral 

 form, exactly resembling small snail-shells, and in fact they were at first taken for the shells of 

 small fresh-water mollusca. They appear generally to live in the water, but Professor Von Siebold 

 found them at Lugano, in Italy, under dead leaves in a wet rocky spot. 



The case formed by the larvae of the Leptoceridae is usually a cylindrical, slightly curved 

 tube, composed of sand-grains, to the surface of which long twigs are sometimes attached. The 



larvae live both in standing and running water, 

 but generally avoid strong currents. The case of 

 the larva of Molanna angustata, a British species, 

 which usually inhabits standing water, is described 

 by Mr. McLachlan as follows : " It consists of an 

 inner tube, but the external aspect is very broad 

 and flattened, convex above, with the head-end 

 produced far over the termination of the tube, 

 forming a cover partially protecting the larva when 

 feeding; beneath, the case is slightly convex in the 

 tubular portion, but the sides are dilated in a 

 concave manner. The material employed is fine 

 sand, but to the outside of this, above, are fixed 

 large angular flakes of silex, and, more rarely, 

 vegetable fragments." This larva always lives 

 upon a sandy bottom, where its case is very diffi- 

 cult to detect unless the inmate moves. Two 

 British species of Setodes (S. tineiformis and 



interrupta) live in cases composed solely of hardened silken secretion, with no sand or otiier extra- 

 neous matters attached to them. 



Of the Hydropsychidae, the larvae live both in standing and running water, but more 

 commonly in the latter, and they appear to be to a great extent carnivorous in their habits. 

 Their cases are free, usually consisting of irregular oval masses of small stones, attached to 

 the surface of larger stones at the bottom of the water. Sometimes the larvae live gregariously 

 under a common roof, composed chiefly of vegetable debris fastened together with silk, but then 

 they make separate cases in which to pass the pupa state. The species of the genus Tinodes, 

 and some others, make silken galleries upon the surface of submerged stones, &c. 



The Rhyacophilidae, which include many species, especially in the typical genus RhyacopMla, 

 agree with the preceding in their general habits, and many of them frequent torrents. The pupa 

 is enclosed in a special brown cocoon within the case. 



Finally, the Hydroptilidae, which include a great number of very minute species, some of 

 them barely an eighth of an inch across the wings, make little cases of silk resembling seeds, to 

 the outer surface of which a few minute sand-grains, portions of diatoms, &c., are attached. 

 These cases have a slit at each end, and the larva can protrude its head at either of them. The 

 larvae inhabit both standing and running waters. 



W. S. DALLAS. 



XARVA (A), LARVA-CASS (u), COCOOX (c), PUPA (D) 

 IMAGO (E), OF RHYACOPHILA VULGARIS. 



