ORDER LEPIDOPTERA 67 



The larvae of the second group of Lithocolletis, the 

 Cameraria group, loosen the upper epidermis of the leaf. 

 After their third moult their head capsules and bodies are 

 still very much flattened and instead of having the head 

 then at a slightly oblique angle to the body as in Litho- 

 colletis proper, it continues to lie in the same plane. This 

 structural difference is accompanied by a difference in 

 habit. Instead of feeding within the limits of the mine 

 already made they go on increasing the area of the blotch 

 (or gallery as it may be) by eating further into the leaf, 

 now ingesting thin slices of the tissue instead of merely 

 shearing through cells to take their sap. One often meets 

 certain unique types of mining. The senior author has 

 studied the western sycamore miner, Lithocolletis felinella. 

 The larvae in feeding cut the fibrovascular bundles in such 

 a way that the portions of the leaf beyond the mines remain 

 green after the rest of the leaf has turned brown. 



FRASS DISPOSAL 



If there are advantages to these tiny caterpillars in being 

 shut up within a thinly spread but dependable food supply 

 out of danger from evaporation and from the clumsier of 

 their predaceous enemies, there is also the disadvantage 

 of being close-quartered with their own waste. That it is a 

 disadvantage to them may be guessed from the pains they 

 take to dispose of their f rass ; and the constancy and precision 

 of miners in this respect is one of the best clues to their 

 identity. If the mine be linear the problem is simple. The 

 frass is left in a trail behind; the food is ahead and uncon- 

 taminated. Some miners, usually those making blotches, 

 go to the trouble of making holes for ejecting the frass out of 

 the mine. Thus the species of Cosmopteryx make small 

 round holes at intervals for the purpose. Some species of 

 Tischeria make slits on the lower side of the leaf. Bedellia 

 somnulentella, after making a linear mine as a young larva, 



