overhangs the sclerotized part of the mandible near it; ventral of 2 outer 

 setae of mandibles curved, situated slightly basal or distal to the dorsal 

 seta. 



Pregula forming a transverse sclerite, which is sometimes interrupted 

 in the middle; pregula divided in this case (Orthotrichia). Submentum 

 varying in form, with straight or slightly concave anterior margin; posterior 

 margin curved or with a median process; setae at the sides short or 

 moderately long. Stipes with two sclerites, a small lateral sclerite and a 

 larger ventral sclerite; apical seta shorter or almost as long as the basal 

 seta. Palpiger with a wide lateroventral sclerite; distal seta long and 

 strong; median seta small and thin. First segment of maxillary palp 

 incompletely sclerotized and fused with the galea; segments 2 and 3 with 

 ring-shaped sclerites, sometimes fused; last segment with membranous 

 apex; number of sensillae 3 or 4. Galea partly sclerotized on the inner side 

 and ventrally at the base, with characteristic sensillae and setae. Setae 3 

 and 6 of galea situated ventrally; setae 4, 5, 7, 8 and 9 situated dorsaily; 

 last 4 setae forming a longitudinal row; lateral sensilla of the galea of 

 group I is inflated apically; it is always present, sometimes very long 

 317 (Orthotrichia); median sensilla present only in Oxyethira; 2 ventro- 

 distal sensillae of group II setuliform; the distal of the 2 sensillae of 

 group III are situated in the middle, the apical sensilla is two-segmented; 

 the basal sensilla is sometimes club-shaped (Figure 394). 



Mentum forming a curved, transverse sclerite with a deep notch at the 

 anterior margin; posterior margin of sclerite covered by the membranous 

 fold of the submentum; Small, ventral sclerites rounded or slightly oblong, 

 with a very short seta; labial palpifer relatively large, sickle -shaped, with 

 anteriorly extending mediodistal ends. Labium short, slightly laterally 

 compressed, sometimes flattened in the basal part (it hy t r i c hi a); the 

 one -segmented labial palp with two terminal sensillae. 



The thoracic segments differ little in size; metathorax usually broader 

 than the other segments. Nota of all 3 segments sclerotized; pronotum in 

 the 5th-stage larva completely covering the segment anteriorly, but the 

 anterior margin of meso- and metathorax remain membranous (as in the 

 young larvae). Pronotum always extending farther laterally than the 

 sclerites of meso- and metathorax and sometimes more strongly curved, 

 resembling part of a circle or ellipse in cross section. Median suture of 

 dorsal sclerites of thorax sometimes diverging at the end, forming a small, 

 wedge-shaped notch; this suture is sometimes (A gray lea) not as clearly 

 marked on meso- and metanotum as on the prothorax, and may be absent in 

 the weakly sclerotized posterior part of the metathorax. Anterior angle 

 of pronotum rounded; its posterior margin forms a ridge or groove; angles 

 of sclerites of meso- and metathorax usually sharply marked. 



Primary anterior -margin seta of pronotum displaced posteriorly toward 

 the middle setae, forming a transverse row of 4 setae arranged in pairs 

 (setae 1 and 2, 3 and 4); in some genera, seta 5 stands near the former 

 group and seta 6 near the latter group. Near the anterior margin of the 

 pronotum are 3 series of secondary setae which develop from the 2nd stage 

 onward: l) 3 long and thick setae of group M; 2) groups of short, thin, 

 anteriorly curved yellow setae (m); 3) very small setae situated between the 

 groups M and m. In the anterior angles of the sclerite, near the long, 



346 



