152 LEAF-MINING INSECTS 



Concerning the bulrush leaf -miner, A . robusta, Miss Braun 

 (21) writes: 



The larvae begin to mine early in April. The mine extends 

 toward the tip of the leaf, beginning as a small transparent blotch, 

 with an opening on the under side of the leaf; following this is a 

 linear green portion with sides nearly parallel, in which the leaf 

 substance is not eaten ; beyond this the mine expands and becomes 

 larger and semi-transparent. When ready to pupate, the larva 

 leaves the mine through a circular hole in the upper side of the 

 linear green portion. Larva whitish with head black, thoracic 

 plate dark brown, a brown spot on posterior half of 9 and anterior 

 half of 10. The imagoes emerge in early June. 



DOUGLASIIDAE 



The little that is known concerning the few leaf miners of 

 this small family is contained in brief and scattered notes on 

 Europaean species; and these notes indicate merely that 

 the larvae are miners during their earliest instars in the 

 leaves of Rosaceous plants, such as strawberry and rasp- 

 berry. 



HELIOZELIDAE 



The larvae of this small family are tissue-feeders that 

 eat out the mesophyll rather completely from their small 

 blotch mines, and fill a considerable part of them with their 

 rather voluminous frass. When fully grown they construct 

 lenticular cases from the epidermis of the newer clean por- 

 tion of the mines, and pupate within these cases. They 

 leave the mine only when they are full-fed . None are known 

 to be case-bearing from the beginning. 



The larvae are strongly flattened. They have neither 

 segmented thoracic legs nor prolegs with crochets, but 

 Coptodisca has pairs of little sucker-like discs on thoracic 

 segments two and three, and is able to carry its case some 

 distance before pupating. The pupa has segments 2 to 7 

 free. 



