36 



ARKIV FÖR ZOOLOGI. BAND 8. NIO 9. 



Lyonetia. 



In L. clerckella L. the labium is of the same type as in 

 Cemiosto?na, as regards the development of the hypopharynx. 

 the backward situation and small size of the spinneret, and 

 the labial palpi. 



Elachista and Nepiicula. 



These two genera represent quite a different line of de- 

 velopment of these organs. 



When an organ becomes 

 useless, it undergoes either a 

 more or less complete reduction, 

 or it saves its existence by 

 adapting itself to another func- 

 tion. 



In the genera, the mouth- 

 parts of which we have describ- 

 ed above, we see the former 

 alternative more or less realized, 

 the spinneret and the palpi 

 having undergone a partial re- 

 duction. In Elachista and Nep- 

 ticula, on the other hand, these 

 organs still retain their places 

 far forward, and form the floor 

 of the mouth-opening, but the 

 labium has modified its shape 

 and function to a considerable 

 extent, besides retaining some 

 features which are probably primitive. 



In Nepticula (figs. 55 a & b) the spinneret is shaped as a 

 thin spade-like organ, slightly narrower at the base and 

 truncate at the top. The palpi are 2- or 3-jointed, depending 

 on whether the narrow horn-shaped terminal joint be con- 

 sidered a joint or a bristle. In my opinion it is, from a com- 

 parison with the palpi of other genera, evident that if they are 

 2-jointed these two joints do not correspond to the two joints 

 of other larvse, but to the two proximal joints of Eriocrania 

 (fig. 48), the terminal joint in Nepticula being the one which 



56. 



Fig. 56. Submentum, mentum, 



labium and left maxilla of 



Elachista sp. X 363. 



