SUPERFAMILY NEPTICULOIDEA 87 



Some become blotched after the larva has reached the third 

 and last instar; some few are blotched from the beginning. 

 The earliest part of the mine is often so small as to be diffi- 

 cult to follow, save perhaps the faint line of excrement that 

 leads back and back and even into the withered bit of egg 

 covering on the surface of the leaf. 



The pupa. When the larva is full-fed it cuts a semi- 

 circular slit in the epidermis and crawls out of the mine. 

 In rubbish or in surface soil it spins a characteristic cocoon. 

 This may be of whitish, yellowish, brownish, or greenish 

 silk according to the species. Traegardh has pointed out 

 that the cocoons of some, and probably of all, Nepticulids 

 have a very novel and interesting device for enabling the 

 moths to gain their freedom. The silk of the cocoons is firm 

 and tough, and the pupae are delicately chitinized and have 

 no cutting or tearing structures about the head region. 

 That these thin, frail, pupal shells are extruded from the 

 cocoons for the release of the adults depends largely on this 

 peculiarity of the cocoons, namely, that there is a narrow 

 fissure at the anterior end. The edges or lips of this mouth- 

 like opening press firmly together and are forced apart only 

 by the movements associated with the emergence of the 

 adult. Sometimes the borders of the fissure form a pro- 

 jecting rim which may be continued around the entire length 

 of the cocoon. The fissure itself, however, extends only 

 from the anterior end a third of the length down either side 

 and is so inconspicuous that it is not surprising the ingenious 

 arrangement should have escaped the notice of many 

 naturalists. 



The pupae are, as we have said, very delicately chitinized. 

 On the back of the abdomen are patches of small setulae 

 which function in helping the pupal shell to pass out of the 

 cocoon. The appendages are free and segmented. Ab- 

 dominal segments one to seven are apparently free and 

 mobile. The pupal form is flattened and ovate. In the 



