9 INTRODUCTION 



LARVA 



General description 



The structure of the larvae of Trichoptera is distinctly primitive. The 

 body is very elongate; its division into head, thorax and abdomen is distinct; 

 the thoracic and abdominal segments are not fused and are well separated. 

 The mouth is directed forward or more or less downward; the mouthparts 

 are of the biting type and are well developed. The prothorax is usually 

 more strongly sclerotized than the two following segments. The legs are 

 of the walking type; the hind legs are rarely swimming legs. The abdomen 

 consists of nine segments; the ninth segment bears the anal legs. The 

 integument of the abdomen is soft and membranous except for small 

 sclerites and sclerotized points. All abdominal segments bear small 

 tergites in some species of Hydroptilidae. The anal legs have a short stem 

 with a thick terminal claw; they are characteristic for the order. 



The larvae are 2 — 3 to 50— 60mm long; the smallest larvae occur in the 

 family Hydroptilidae, which includes dwarf forms; the largest larvae are 

 characteristic for species of the genera Himalopsyche (Rhyaco- 

 philidae) St enop s y che (Stenopsychidae), Phryganea (Phryga- 

 neidae), Dicosmoecus, Nemotaulius, Gr am m ot a u 1 i u s, Pota- 

 mophylax, Hydatophylax (Limnophilidae). 



The sclerites usually bear a pattern of stripes, spots and dots; the dots 

 are pigmented or not pigmented points of the attachment of muscles to the 

 inner wall of the sclerites; the outline of the dots may be distinct or 

 diffuse. The pattern often varies in the species, but it is usually a reliable 

 diagnostic character. 



The hard and soft parts of the integument bear setae which often change 

 markedly during metamorphosis and appendages of a different type. The 

 number of primary setae on certain parts of the body is constant throughout 

 the order; secondary setae occur in smaller or larger numbers in various 

 groups. The chaetotaxy is an important diagnostic character of families, 

 subfamilies and genera. The chaetotaxy of species varies sometimes to 

 some extent. 



The division of Trichoptera into two suborders is clearly marked 

 morphologically and biologically in the larvae. The suborder Annulipalpia 

 is characterized by campodeiform larvae* with a prognathous head, deep 

 constrictions between the abdominal and thoracic segments, and usually 

 with long anal legs which bear a claw that is diverted anteriorly and downward 

 (Figure l); the larvae are either free-living or they live in movable cases 



* The name "campodeiform" indicates a resemblance to species ofCampodea (order Thysanura). 



