The families Arctopsychidae and Hydropsychidae are the most specialized 

 groups of Annulipalpia; however, the larvae of these families retain a 

 number of primitive characters which unite them with some lower groups. 

 Such are the simple prognathous head of Arctopsychidae with its primary 

 chaetotaxy; the free trochantin; the simple claw of the anal legs which 

 resembles that of Psychomyiidae. We also consider the sclerotized meso- 

 164 and metanotum (as in Ecnomidae and Hydroptilidae) as primitive characters 

 retained in the higher Annulipalpia together with their general high 

 specialization. The predatory larvae live in narrow chambers (the most 

 skilfully built chambers of the whole suborder), waiting for the prey, which 

 they capture in netlike screens. The larvae are mobile, but live in a narrow 

 space, which possibly contributed to the retention of the dorsal sclerites of 

 the thorax. The Arctopsychidae are more primitive: as in the Polycentro- 

 podidae, the head is slightly elongate; the position of the tentorial pits is 

 normal; the frontal sutures are curved at the point of the tentorial pits; 

 there are only primary setae on the head, while the Hydropsychidae are the 

 only family of Annulipalpia in which some genera have a large number of 

 secondary setae on the head. The sclerotization of the meso- and metanotum 

 of Arctopsychidae is slightly interrupted; the tergites of the segments are 

 divided into 2 parts by a transverse suture, which increases flexibility. 

 Both families are highly specialized in all other characters: 



1) a rich development of the secondary chaetotaxy of the legs and anal 

 legs; long setae form typical groups at the base of the claw of the anal 

 legs of the larvae; 



2) the cutaneous appendages of the larvae are very complex; in the 

 sclerotized parts of the body, the generally small covering setae have a 

 very diverse form, from long setae on the sternites of segments 8 and 9 to 

 various forms of minute needle-shaped cylindrical, stellate, tuft- and feather- 

 shaped setae on head, thorax and legs; the membranous areas of the 

 integument are also covered with small, dark covering setae; 



3) the presence of characteristic ventral sclerites on abdominal segments 

 8 and 9, which are absent in all the other families; these sclerites bear 

 posteriorly directed, strong covering setae which support the larva during 

 its net weaving (see Figure 12 7). 



According to the prevalence of primary or secondary chaetotaxy, the 

 Annulipalpia are divided into 2 superfamilies: the Paleochaetoidea Lepn., 

 and the Neochaetoidea Lepn. (Lepneva, 1956:14—21). These 2 groups differ 

 in their method of feeding, mode of life, the structures they build, their 

 general morphology and the chaetotaxy. Primitive characters predominate 

 in the Paleochaetoidea, specialized characters in the Neochaetoidea. The 

 Paleochaetoidea include the Rhyacophilidae, Glossosomatidae, Hydroptilidae, 

 Philopotamidae, Stenopsychidae and Psychomyiidae; to the same group also 

 belong the tropical American Xiphocentronidae, the larvae of which are 

 closely related to the Psychomyiidae. The Neochaetoidea include the 

 Ecnomidae, Polycentropodidae, Arctopsychidae and Hydropsychidae. All 

 Neochaetoidea are predators; the last 3 families of the group build capturing 

 nets; the Ecnomidae weave simple tunnel- shaped tubes; they are predators 

 which live in primitive tubular structures like the higher Paleochaetoidea; 

 the secondary chaetotaxy of the Ecnomidae larvae is less well developed 

 than in the 3 higher families of the Neochaetoidea. The Ecnomidae are the 



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