primitive Phryganopsychidae, the mesonotum is completely sclerotized. 

 In the Molannidae and in the Arctopsychidae the mesonotum is divided by a 

 transverse suture; the whole metanotum of Leptoceridae is membranous 

 and the mesonotum is incompletely developed; it is reduced in some species 

 to 2 small longitudinal rods. The Limnophilidae retain rudiments of the 

 metanotal sclerites in form of small or larger sclerites; they also 

 sometimes retain tergal sclerites of the 1st abdominal segment. 



To summarize the foregoing and the data in the systematic chapter, and 

 160 to give a general picture of the phylogeny of the Annulipalpia based on data 

 of preimaginal stages, we enumerate below the characters considered 

 primitive. 



Full-grown larva 



1. Small* or moderate size of the full-grown larvae with a general or partial resemblance to the lst-stage larva. 



2. A slightly flattened and elongate head. 



3. Simple mouthparts with short mandibles with small denticles. 



4. Deep constrictions between the body segments, which are of similar form. 



5. All 3 pairs of legs are about the same length and form. 



6. The dorsum of the thoracic and abdominal segments bear small sclerites of similar form. 



7. The primary, primitive, unspecialized chaetotaxy consists of relatively long abdominal setae. 



8. The moderately developed anal legs have a simple, short, curved claw. 



9. There is no portable case. 



10. The larvae live in tubular trenches in slowly flowing water. 



11. The larva is microphagous. 



Pupa 



1. Absence of anal lobes or rods. 



2. Presence of a well-marked pupal cocoon. 



The primitive character of the family Rhyacophilidae (except the 

 Glossosomatinae) is generally accepted. The adult Rhyacophilidae have a 

 primitive wing venation and a short life (only a few days); they lead an 

 especially concealed mode of life hiding during the day near the shore in 

 deep cracks among stones or near the base of dense shrubs. They do not 

 feed and do not swarm; they die after copulation and oviposition. The 

 larvae of this large family (over 300 species; Ross, 1956:115—126) are 

 small, medium- sized or large in the later stages, leading a mobile life in 

 rapidly flowing streams; they include species which are morphologically 

 specialized within limits of the primitive structure of most of their organs, 

 and within limits of the retention of their primary chaetotaxy which is 

 completely primitive and poorly differentiated in the lowest forms 

 (Hy p o r hy a c o ph i 1 a group). The latter group includes species of 

 Rhy ac ophila, the full-grown larvae of which have slightly flattened, 

 subcylindrical and gill-less segments, with simple primary setae on the 



The fossil Trichoptera of the deep Mesozoic and Permian were small (wing length 2.7— 3.5 mm). 



150 



