86 



LEAF-MINING INSECTS 



at first confine their feeding to the single layer of palisade 

 tissue next the cuticle. As they become larger a part of the 

 spongy parenchyma also is consumed. 



The larva. The larvae are slightly flattened with the head 

 deeply retracted into the thorax. Jointed thoracic legs and 

 crochets are wanting and locomotor appendages are repre- 

 sented only by roughened protuberances. Such projections 

 are to be found in pairs on the second and third thoracic 

 segments and on the second to seventh abdominal ones. 

 Some species are said to have one or two additional pairs. 



a 



Fig. 32. Typical mines of Nepticula. (From Miss Braun.) 

 pallida; b, N. yomivorella; c, N. nyassaefoliella; d, N. saginella. 



Miss Braun has ascertained that there are four larval 

 instars and has made some observations on the relative 

 amount of feeding in the various stages. The mine formed 

 in the first instar rarely exceeds a few millimeters in length 

 while the area mined in the last instar is usually much more 

 than half the total area of the mine. She found that the 

 larva of Glaucolepis saccharella remained in the mine more 

 than sixteen days. In this species second and third moult- 

 ing periods each took from thirty-six to forty-eight hours. 



The mines as a rule are linear and serpentine but with the 

 very many species of Nepticula comes considerable diversity. 



