XXI CADDIS-FLIES 483 



large funnel-shaped verandah, covered by a beautiful sillcen net. 

 This larva lives in the rapids of various rivulets, and the entrance 

 to the verandah is invariably directed towards the upper part of 

 the rivulet, so as to intercept any edible material brought down 

 by the water. Several of these larvae, moreover, build their cases 

 so that they form a transverse row on the upper side of a stone ; 

 as many as thirty cases may be placed in one of these rows, and 

 sometimes several rows are placed parallel with one another. 

 This same larva has the habit of coming out of its case when 

 necessary, and suspending itself in the water as some caterpillars 

 do in the air by means of a silken thread. Other members of 

 the Hydropsychides form tubes or covered ways of silk, earth and 

 mud attached to stones, and in which they can move freely about. 

 Some of the Hydropsychidae have been ascertained with certainty 

 to be carnivorous in the larval state. A species of the genus 

 Hydropsyche has been found by Howard^ to help itself in the 

 task of procuring food by spread- 

 ing a net in the water in con- 

 nexion with the mouth of its 

 case. This net is w^oven in wide 

 meshes with extremely strong 

 silk, and supported at the sides 

 and top by bits of twigs and 

 small portions of the stems of 



water - plants. Small larvae ^ig. 328. Case, with head of larva and 



-, 1 J. 1 1^1 . snare of North American Hydropsy- 



brOUght down by the current chid. (After Kiley and Howard.) 



are arrested by this net for 



the advantage of the larva that lurks in the tube. The 

 breathing organs of the larvae of Hydropsychides are apparently 

 of a varied character, and would well repay a careful study. Mr. 

 Morton informs the writer that some of our British species of 

 Fhilopotamus and Tinodes have no gills either in the larval or 

 pupal state, and probably respire by means of modified tracts in 

 the integument. In some of the allied genera, e.g. Poly centr opus, 

 the larvae are destitute of gills, but the pupae possess them. 



The Rhyacophilides is another group in whicli the larval 

 habitations are fixed. Some of these larvae have no respiratory 

 filaments, breathing only by means of the stigmata, but others 

 have tufts of filaments. These Insects have a peculiarity in their 



^ Rep. of the Entomologist, 1886, p. 510, Washington. 



