The number of primary setae on the abdominal segments is the same 

 as on the thorax, but their arrangement and shape are different; the abdomi- 

 nal setae, especially in case-bearing larvae, are much shorter than the 

 thoracic setae. Of the 5 dorsal setae* of the abdominal segments, the seta 

 in the anterior corner is markedly displaced posteriorly (it retains this 

 designation as it is homologous to the corresponding seta of the thoracic 

 segment); in a number of forms the seta at the anterior margin is much 

 reduced in size and thin, sometimes only a hardly noticeable setule; the 

 same is often the case with the intermediate and lateral surface setae which 

 are much shorter than the anal seta at the base of which they are situated. 



The seta in the anterior angle and all 3 surface setae on the dorsum of 

 segment 9 are displaced posteriorly and arranged in a row; if a tergite is 

 present, it is situated at the posterior margin; the seta at the anterior 

 margin either remains in its place in the form of a setule, or is also 

 displaced toward the surface setae, slightly anterior to them (Figures 11 

 and 12). In the pleural region, 2 small setae are arranged in a row, one 

 behind the other. Ventrally, there are 3 setae on each side; on segments 2 — 7 

 these small setae form a transverse row in which the median seta is longer 

 than the other two; there are 3 setae on segment 9 and the lateral seta may 

 be displaced to the pleural or even dorsopleural region. ** 



Anal legs. The posterior margin of abdominal segment 9 bears the 

 anal legs (postpedes), or claspers. t The anal legs differ in shape, according 

 to the mode of life and movement of the larva. In free -living larvae, the 

 anal legs are long, flexible, with the structure of walking legs; the larva uses 

 them to support the posterior end of the soft body. Eruciform larvae living 

 27 in cases use the thoracic legs for movement, while the anal legs are only 

 for holding the case and for movement inside the case; the anal legs of such 

 forms have the form of short crotchets and deserve the name claspers. 



In spite of the differences in the appearance of this highly specialized 

 organ caused by its adaptation to different tasks and mode of movement, the 

 anal legs of the caddis fly larvae are built according to the same plan in the 

 whole order. 



The main part of the anal leg consists of a basal part ("a"), a medial 

 part ("b") and an apical part ("c")tt (Figure 13); part "a" is present in the 

 long anal legs of the larvae of Annulipalpia (except Rhyacophilidae, 

 Glossosomatidae and Hydroptilidae); it is always soft, not sclerotized, and 

 in some groups divided by a fold into two parts by a transverse skin fold; 

 part "b" bears a long dorsolateral sclerite; the claw of the leg is movably 

 attached in two points at the distal end of the sclerite; part "b" bears 

 4 primary setae; the sclerite of part "c" has a ventrodistal position; it 

 usually bears one seta, rarely two. 



The claw has a basal margin with two dorsal articular processes and a 

 ventral process to which the adductor muscle is attached. It is divided into 

 a basal part and the claw by a membrane; this membranous groove extends 



• Only the setae of one half of the segment are described. 

 ** In addition to the primary setae, the abdominal segments bear one or two presegmental setules dorsally 



(Nielsen, 1942:300). 

 t The anal legs are paired appendages of the 9th segment; they are present already in the embryo; Krafka's 



opinion (1924:99—102) that the basal part of the legs consists of the divided 10th segment was refuted by 



Nielsen (1942:309). 

 tt These parts are marked with Latin letters from comparative morphological studies (Nielsen, 1942:306—311). 



23 



