102 LEAF-MINING INSECTS 



entrance hole or they return to it to eject excrement. In 

 passing over the leaves they hold to the surface by threads 

 which they spin on the leaves about the mined area. In 

 changing to a pupa they attach themselves by their anal 

 extremities to a junction of such threads and are held in a 

 more or less horizontal position upon other cross threads by 

 dorsal recurved bristles. The adult is a yellow moth having 

 a wing expanse of two-fifths of an inch. 



Leucoptera and Proleucoptera are closely related genera. 

 The first species of this group to be reared in this country 

 was probably Leucoptera albella. It attacks several species 

 of poplars and willows and has a wide distribution. Cham- 

 bers reared it in the Ohio valley. Dyar found it attacking 

 particularly the narrow-leaved cottonwood, Populus angus- 

 tifolia, in Colorado. The mines are large black blotches 

 frequently involving the whole leaf. The larvae are gre- 

 garious, a single leaf and mine being shared by several in- 

 dividuals. The abundant black frass is contained in the 

 mines. It appears that there are at least two generations 

 a year. The larvae being abundant in June and again in 

 September in the transition zone. When they are full-fed 

 the larvae emerge from the leaves and on the lower surface 

 spin bands or cables of purest white silk. They then make 

 flat, oval, white cocoons between the cables and the leaf 

 surface and transform to pupae. Leucoptera pachystimella 

 attacks the old leaves of the evergreen plant, Pachystima 

 myrsinites, in western North America. The mines are at 

 first linear and follow the margin but later they expand into 

 a blotch which involves the whole of the surface of the 

 small leaves. The frass is contained in the leaf but is 

 packed rather firmly into one end of the mine. The cocoon 

 of this species, like that of the preceding, is spun between 

 bands of silk and the lower surface of the leaf. 



Proleucoptera smilaciella as an adult is an exquisite little 

 moth, clad in ermine and decorated with gold and silver and 



