bears one, in the Integripalpia usually 2 small primary setae on the outside. 

 The stipes form the broad middle part of the maxilla; it bears an oblique 

 narrow or well-developed ventrolateral sclerite with 2 primary setae, a 

 shorter distal seta and a longer proximal external seta. Inside the preoral 

 cavity, longitudinal grooves separate the submentum from the stipes of the 

 maxilla; there is a tubercle covered with thin hairs near the distal margin 

 of the stipes in many forms which is developed in some species ofHalesus 

 and Silo into a distinct lacinia with a small basal sclerite (Nielsen, 

 1942:285); the lacinia is absent in many forms, even as a rudimentary 

 tubercle. 



The distal part of the stipes reaches the palpifer with the galea and 

 four- segmented palp. The palpifer bears two sclerites: a lateral sclerite 

 which extends ventrally, externally and partly dorsally, and a small medial 

 sclerite; the lateral sclerite bears 2 setae, one at the anterior margin and 

 one at the inner margin which is much smaller than the anterior seta. 



The galea of predators (Rhyacophilinae, Polycentropodidae) is completely 

 sclerotized and cylindrical with a membranous distal margin; the galea is 

 short in a number of forms and in others (Agapetus, Apatania, Silo) 

 it is reduced to a small tubercle. The galea bears setae and sensillae 

 (Figure 7, B); Annulipalpia have 7 setae with the numbers 3-9 (following 

 setae 1-2 of the palpifer); the galea of Integripalpia bears 4 setae, 

 numbered 6 to 9 (the palpifer of this suborder bears setae 1—5); setae of 

 the galea are often lost; there are 3 pairs of sensillae numbered I— III. In 

 addition to the above sensillae and setae which are constant for the order, 

 palpifer, galea and lacinia of a number of groups are recovered with 

 numerous thin hairlike setae. 



The palp consists of four segments with crescent- shaped or annular 

 sclerites; these sclerites bear one or two minute light pits; the palps may 

 be long or very short; the tip of the terminal segment is membranous and 

 bears sensillae. 



The labium (Figure 7) consists of the second, fused pair of maxillae; 

 it forms the labial lobe* together with the mentum. The labial lobe forms 

 a more or less long ligula. The mental sclerite surrounds this part 

 ventrally, laterally and partly (sometimes completely) dorsally in some 

 forms; the mental sclerite is divided into two halves in some groups by the 

 membranous ventral suture. On the labial part proper, two small, rodlike 

 sclerites, each of which bears a small seta are situated distal to the mentum; 

 these sclerites are called the ventral sclerites or the ventral rods. At the 

 20 base of the labial palps are the small sickle- shaped sclerites of the labial 

 palpiger; each sclerite bears a pit. The labial palp consists of one segment 

 with three terminal sensillae; it is sometimes very small, rudimentary and 

 sometimes absent (Psychomyiidae). 



Thorax. Prothorax, mesothorax and metathorax of the larvae of caddis 

 flies are always distinctly differentiated and more or less sclerotized. 

 There are sclerites of two types on the dorsum:** large sclerites (nota or 

 terga)* which occupy the whole dorsum or most of it, and small tergites in 



* The distal part of the organ, without the mentum, may be called the labial lobe proper (eulabium), while 

 the more basally located medial area of the gula-mentum may be considered as consisting of the gula, 

 pregula, submentum and mentum. 

 ** We distinguish between the prodorsum, mesodorsum and metadorsum. 



t We distinguish between the pronotum, mesonotum and metanotum, which are the sclerites of the prodorsum, 

 mesodorsum and metadorsum. 



16 



