240 



Denning: Trichoptera 



Fig. 10:3. Representative Trichoptera cases and larvae, a / fa, Leucorrichi'o pictipes; c, Leptocella 

 albida; d, Triaenodes tarda; e, Hel icopsyche borealis (Ross, 1944). 



shut to form the pupal chamber. Not all Hydroptilidae 

 have cases of this type, some of them having true 

 cases (fig. 10:3a, b). 



"Case Makers. — All caddisfly larvae except those 

 listed above make portable cases which the larvae 

 drag with them in their daily movements. These cases 

 are usually made of pieces of leaves, bits of twigs, 

 sand grains or stones which are cemented or tied 

 together with silk. Rarely the case is made entirely 

 of silk. Case construction varies a great deal from 

 one group to another, from one species to another 

 within the same genus, and frequently within the 

 same species. In general, cases subject to greatest 

 stream current are the most solidly constructed, 

 whereas those in small ponds where there is scarcely 

 any water movement are the most loosely constructed. 



"For pupation the case is anchored to a support 

 and a top added to the case; the pupa is formed inside 

 this shelter and no additional cocoon is made." 



The cases constructed by the larvae are of many 

 kinds and of such materials as sand, sticks, leaves, 

 and shells. The case-building larvae are phytophagous 

 whereas the free-living larvae are carnivorous. Repre- 

 sentative larval cases are illustrated in figures 10:2; 

 10:3. 



SUGGESTIONS FOR COLLECTING CADDISFLIES 



Adult caddisflies are secretive, highly excitable, and 

 wary. During the day they seek cool, dark, damp 

 situations, and seldom fly actively until dusk. Their 

 movement, whether in flight or running about on a 

 surface, is rapid and jerky, and collecting is often 

 rather difficult. For most productive collecting it is 

 necessary to find their daytime resting places. These 

 are wooden bridges, especially in mountainous areas, 

 when the underside is dark and cool; concrete highway 

 bridges; vegetation along the water's edge; vegetation 

 hanging over water; and branches of shore-line conif- 

 erous trees. A lone coniferous tree along an open 

 stretch of the bank will often yield an abundant 

 variety of adults. Caddisflies may be also found in 

 crevices of bark, under ledges, or in protected parts 

 of buildings — especially if near water. The adults 

 may be collected resting on vegetation, stones, or 

 exposed sticks in the water. Sweeping or beating is 

 the best method for dislodging adults from vegetation, 

 and a cautious approach with an open killing bottle 

 is effective for specimens resting on an open surface. 

 On warm, cloudy nights with little or no wind, 

 large numbers of adults may be taken in flight. They 



