34 



ARKIV FÖR ZOOLOGI. BAND 8. NIO 9. 



Cemiostoma. 



Of this genus I have had material of two species, C. labur- 

 nella St. and G. scitella Z., which is fortunate, since the dif- 

 ferent species differ in the structure of the mouthparts. 



In them we can easily follow another step in the course 

 of modification of the mouth-parts, which we have traced 

 in the genera mentioned above. 



Thus in a young larva of C. scitella we notice that the 

 hypopharynx projects as a large, finely hairy tongue towards 



53. 



Fig. 53. Cemiostoma laburnella. Submentum, labium and left maxilla 



of young larva. Ventral aspect. 

 Fig. 54. C. laburnella. Old larva, spinneret and labial palpi. X 417. 



a level with the palpiger, whereas of the spinneret and the 

 labial palpi all that remains is a pair of very small, scarcely 

 discernible hairs (fig. 53). 



In an older larva, on the other hand, we find both spin- 

 neret and palpi, but they are greatly reduced in size in com- 

 parison with typicai larva?, and have moved still further 

 backwards, being placed behind the middle of the stipes. 



The spinneret is very short, as are also the palpi, which 

 are single-jointed, truncate at the top, where they are pro- 

 vided with two hairs. The base of the spinneret is anteriorly 

 surrounded by a horsehoe-shaped plate, with a pair of rounded 



