addition to the large sclerites or replacing them. The large dorsal sclerites 

 usually consist of two halves separated by a median longitudinal suture;* 

 there is rarely a transverse suture which divides each sclerite into an 

 anterior and posterior part. The sclerotization of the thorax differs in the 

 various families. In four families of Annulipalpia the nota of all three 

 thoracic segments bear almost equally developed sclerites; in the other 

 families of this suborder, only the pronotum is completely sclerotized, while 

 the mesonotum and metanotum are not sclerotized (Figure l) or, as in the 

 Agapetinae, bear only small paired tergites. In species of Integripalpia 

 living in tubular cases, the dorsal sclerotization of the thorax decreases 

 posteriorly. When the larva moves, the prothorax projects completely from 

 the case; it possesses a well-developed pronotum; a large mesonotum is 

 also present in the larvae of Integripalpia except in the Phryganeidae, but it 

 is not as well developed as the pronotum; in the Leptoceridae, Molannidae 

 and some other families the mesonotum covers only part of the mesothorax, 

 and part of the mesothorax is membranous; in families of Integripalpia in 

 which the metanotum is sclerotized, the sclerotization consists of various 

 arrangements of small tergites (Figure 2). 



The form of the pronotum (Figure 8) varies markedly in the different 

 families. The anterior angles of the pronotum may be rounded or rectangu- 

 lar; in other cases they have pointed, anterior processes (Goeridae). The 

 pronotum is always more or less convex; the anterior third of the pronotum 

 is separated from its other part by a transverse groove in some groups; a 

 deeper groove separates the often thick posterior margin and partly the 

 lateral margin; the ridge of the lateral margin forms processes which 

 articulate with the sclerites of the pleural region. The posterior angle of 

 the pronotum forms a lobe which is sometimes so long that it extends to the 

 lateral and ventral surface and is even, sometimes fused in the middle of the 

 ventral surface with the lobe of the opposite side, so that the pronotum is 

 closed. The anterior margin of the pronotum continues into a thick, some- 

 times slightly sclerotized membrane connecting the prothorax with the head; 

 this membrane is folded under the anterior margin of the pronotum which 

 sometimes projects to such an extent that the head may be deeply retracted 

 beneath the pronotum. 

 21 The mesonotum (Figure 9) is less convex than the pronotum; it is almost 

 flat in forms in which it is incompletely developed; its posterior margin is 

 thickened. 



If tergites are present on the metathorax they are of very diverse form. 



The nota of each of the three thoracic segments bear 5 pairs of primary 

 setae (Nielsen, 1942:298); each half of the notum bears one seta on the 

 anterior angle, one on the anterior margin and 3 on the surface (a medial, 

 intermediate and lateral seta). This arrangement is well marked also on the 

 unsclerotized segments of Annulipalpia. This arrangement is usually 

 disturbed on the pronotum: the seta of the anterior margin is displaced 

 toward the surface setae, or the surface setae (especially the lateral setae) 

 are displaced toward the anterior margin of the pronotum; there are 

 secondary setae which are present in small numbers on the pronotum even 

 if the primary chaetotaxy is retained on the other thoracic and abdominal 

 segments during all larval stages; the secondary setae of the anterior 

 corner of the segment are especially constant; there may be one, two or 

 more. 



* The medial suture is absent in the first larval stage. 



17 



