its base; the setae are connected with the cuticle by a thin annular membrane; 

 the alveoli are surrounded by a thickened ridge which is sometimes dark. 

 There are also pits resembling alveoli; these pits are also sense organs, 

 but are without setae (Nielsen, 1942:265). 



The spines vary in size and shape; they may be microscopical spinules, 

 or they are larger, pointed or blunt, standing often close together or are 

 fused at the base, forming combs or star- shaped groups; the larger spines 

 may be short and thick or long, and spear-shaped, thin or thick; the thin and 

 long spines and spinules are setiform and are named "hairlike spinules" or 

 "hairlike chetoids"; they are usually referred to as hairs; the spines and 

 spinules may be divided or branched, bifid, brushlike, stellate, featherlike or 

 bushlike; the light hairlike chetoids on the ventral side of the trochanters 

 and femora in a number of families are usually finely branched like a 

 feather at the margins. 



The setae differ markedly in size and form; the smallest and thinnest 

 light setae are called setulae. The medium- sized and large setae are 

 usually black, dark, medium or light brown, sometimes yellowish; some 

 of them are light, hyaline, e. g., the anterior setae of the labrum, the lateral 

 anterior-marginal seta of the frontoclypeal sclerite in a number of forms, 

 or the ventral setae of the claw of the anal legs. 



The setae present in the first stage larva are called primary setae; they 

 retain this name in all later stages. The number of primary setae and pits 

 is constant (Siltala, 1907:357-361; Nielsen, 1942:265). The setae which 

 appear in the second and later stages are called secondary setae. The 

 secondary setae of the second stage may reach almost the same size as the 

 primary setae at the end of the second larval stage; they are rarely even 

 13 longer; the secondary setae of the later stages are usually shorter than those 

 of the earlier stages; there are thus groups of setae of various size in the 

 mature larvae, corresponding to the various stages. Secondary pits are not 

 formed. 



Secondary setae occur rarely on the head; they always appear on the 

 pronotum; the setae of meso- and metathorax, legs and abdominal segments, 

 in some families remain primary throughout all larval stages, but legs and 

 nota of the thorax acquire a more or less rich secondary chaetotaxy in most 

 groups; secondary setae do not appear on the ventral side of the thorax and 

 on the claws. Secondary setae are also absent on the claws of the anal legs 

 with rare exceptions (Beraeidae). 



The development of secondary chaetotaxy varies markedly in different 

 systematic groups; it is very small in primitive groups but well developed 

 in highly specialized groups. The number of setae is given for only one 

 side of the body in the descriptions. 



Head. The head of caddis fly larvae is an elliptic capsule with a large 

 occipital foramen and a narrower gnathal foramen. The cranium is divided 

 into four well-defined sclerites (Figure 3) by the epicranial and hypocranial 

 or gular sutures; these are the dorsal frontoclypeal sclerite, two lateral 

 sclerites, and the ventral sclerite (gula). The anterior branches of the 

 epicranial suture are called the frontal sutures (sutural frontales); they 

 enclose the frontoclypeal sclerite, and separate it from the large lateral 

 sclerite, the parietal sclerite; these sclerites form the greater part of the 

 dorsal surface of the head, the whole lateral surface and the whole or greater 

 part of the ventral surface. The lateral sclerites are contiguous, posterior 

 to the frontoclypeus along the median epicranial suture, which is called the 



10 



