Annulipalpia) it is also concentrated on the head; the Arctopsychidae have 

 a relatively primitive form, of the head which is slightly elongate and slightly 

 168 flattened with a simple frontoclypeus, and has a notch near the tentorial pits; 

 the head of Hydropsychidae is short, broad, often flattened dorsally; in some 

 forms it has a crown of secondary setae which probably take part in the 

 collection of food from the screenlike nets. In addition to the abundant 

 secondary chaetotaxy (especially on the head of Hydropsychidae), both 

 families have a highly differentiated series of cutaneous appendages in the 

 form of minute covering setae which may be either thin, light, hairlike or 

 short, thick, flattened, branched or sometimes of a peculiar or complex form; 

 this relates these higher Annulipalpia by convergence to some Integripalpia 

 ( Limnophilinae ) . 



The membranization of the body of the mobile predators is especially well 

 marked in the predatory larvae of Polycentropodidae; like the higher 

 Paleochaetoidea, these larvae lost all dorsal sclerites of the abdomen 

 (including tergite 9) and of the meso- and metanotum. The larvae of the 

 3 other families living in a narrower space lost the dorsal sclerites of the 

 abdomen but retained the sclerites of the meso- and metanotum: the 

 Ecnomidae retain them in the form of thin sclerites with a simple primary 

 chaetotaxy, and the Arctopsychidae in the form of sclerites with transverse 

 sutures; the Hydropsychidae retain them in the form of large, hard sclerites 

 approximating this highest family of Annulipalpia to one of the groups of 

 the lower Paleochaetoides (Hydroptilidae). 



Evolution along line 1 of the ancestral stem I took place in the early 

 branches 1' and 1"; these two branches differ in the larvae in the form of 

 the capturing nets, the method of catching prey and corresponding 

 morphological adaptations, especially the development of the secondary 

 chaetotaxy, its distribution on the body and the forms of specialization. The 

 groups which evolved on branch 1" have few cutaneous appendages of the 

 type of small covering setae; they may be called "smooth groups"; the 

 groups which developed on branch 1 ' have a rich development of such 

 cutaneous appendages and may be called "spiny groups." In the recent 

 fauna, each of the foregoing divisions consists of two related families: one 

 is small and very ancient, and one is large and very recent and flourishing; 

 in branch 1", these are Ecnomidae and Polycentropodidae; in branch V, 

 these are Arctopsychidae and Hydropsychidae. 



The small ancient family Ecnomidae is restricted mainly to the sub- 

 tropics and tropics of Eurasia and Africa; the larvae are the most 

 primitive among the Neochaetoidea; its secondary chaetotaxy is little 

 developed and its structures are primitive tunnel- shaped tubes; its 

 ecological range is restricted to water with a slow current or to stagnant 

 water. The large family Polycentropodidae is distributed almost throughout 

 the world; it is an ancient branch which separated from the ancestors of 

 Ecnomidae; it is now highly differentiated and flourishing, which is to a large 

 extent the result of the high morphological specialization of the predatory 

 larvae with its skilfully built capturing nets and its wide ecological range 

 which covers biotopes in small water bodies in caves, various types of 

 flowing water (including large rivers in the plains and stagnant water), 



In the higher Neochaetoidea, which developed on branch l',the Ecnomidae 

 are replaced by the small ancient family Arctopsychidae (about 20 species), 



158 



