42 



ARKIV FÖR ZOOLOGI. BAND 8. NIO 9. 



The labium is shaped like a triangulär, thin, horizontal 

 blade, with rounded anterior margin, excavated in the middle. 

 By a fine, anteriorly concave line, running across at its great- 

 est width, it is divided into two portions, the anterior one 

 of which is finely hairy. This part, I think, we can safely 

 homologize with the hypopharynx, which, as we have already 

 seen in the tissue-feeders, had attained a high degree of spe- 

 cialisation in this direction, and was also characterized by 

 the fine covering of minute hairs. 



The posterior half, on the other hand, is probably con- 

 stituted by the mentum, while the spinneret and labial palpi 

 are completely atrophied, and the only structure remaining 

 is the common duct of the silk glands, which is visible below 

 the cuticle, and ends at the anterior margin of the mentum. 



Lithocolletis sp. 



Fig. 62. Head capsule, ventral aspect (only basal joint of antennse 



delineated). X 155. 

 Fig. 63. Labium hypopharynx, and maxillae, dorsal aspect, X 347- 



In Ornix the retrogressive development of the maxillse 

 has taken another step. In one species, O. pomifoliella (fig. 60) 

 there remains a small projection, representing thepalpus; in 

 another species, O. gultea (fig. 61), even this is atrophied. 

 Lobus externus and lobus internus, on the other hand, are 

 represented by a pair of strong, slightly curved bristles, which 

 in the latter species are longer than in the former, and in 

 both bend slightly upwards. 



The labium, on the other hand, has a more primitive 

 structure, there being a pair of weak hairs left at the end 

 of the salivary duct. 



