or not fully developed; they are not pigmented, or pigmentation is weak; 

 the setae are primary and relatively long, sometimes very long. The form 

 of the larva and the ratio of its individual parts change little from the 

 2nd stage, but the number of secondary setae increases with each stage. 



The postembryonal development varies according to climatic and food 

 conditions; the early stages are shorter than the later ones. In insects 

 with an annual cycle of development, the winter stage is the longest. Some 

 species have two generations per year. From the eggs of the spring 

 generation hatches the summer generation which ends development in a 

 shorter time than the autumn generation; the development of the autumn 

 generation is interrupted by hibernation in one of the later stages and is 

 prolonged. The shortest larval life has been observed in the small species 

 of the family Hydroptilidae; Agraylea multipunctata reaches the 

 5th larval stage 25 days after oviposition (Siltala, 1907:328). 



Together with their growth, the larvae of Annulipalpia increase their 

 shelters and capturing nets; in colonies of N eu r e c lip s i s bimaculata, 

 66 their capturing tubes are easily observed. In the larvae of Integripalpia 

 which hibernate as larvae, growth in winter is slow; growth in spring and 

 early summer is most intensive; the growth is accompanied by adding to 

 the case; according to observations of Hanna (1957a— 1957b; 1959) the 

 growth of the case lags to some extent behind the growth of the larva. 



Building activity 



Shape of the structures. The larvae of caddis flies have well- 

 developed spinning glands and build structures of various types, the form of 

 which depends on the habitat and mode of life of the larvae, their type of 

 feeding and whether they are restricted to a certain biotope. The building 

 activity of caddis fly larvae developed in varying directions and is one of the 

 most important factors that aid in classifying large systematic units and 

 their biological characteristics. 



In the suborder Annulipalpia only the larvae of Rhyacophilinae and 

 Hydrobiosinae do not build structures before pupation; the larvae of 

 Glossosomatidae and Hydroptilidae live in portable cases. However, the 

 larvae of all other families build immovable galleries and nets serving as 

 shelters and for the capture of prey. The simplest type of this structure 

 is narrow, often curved gallery tubes woven by the larvae of Psychomyiidae 

 among slimy incrustations on the bottom, on stones or wood (Figure 95, A); 

 the structures of Philopotamidae, Stenopsychidae and Ecnomldae are similar 

 gallery tubes longer than the larva (Figure 95, B). These larvae collect 

 minute fragments of vegetable and animal food. The predacious larvae of 

 the three higher families of Annulipalpia weave capturing nets which in 

 some species of Polycentropodidae may be 12 — 15 cm long; the entrance to 

 these structures forms a funnel; the larvae of Arctopsychidae and Hydro- 

 psychidae build small shelter chambers and near them screens consisting 

 of regular quadrangular cells (Figure 95, C). 



The portable cases of Hydroptilidae in the later stages are built of silk, 

 rarely interwoven with threads of algae or covered with fine sand or diatom 



5724 60 



