166 LEAF-MINING INSECTS 



This species is unique among leaf miners as it requires 

 two years for its development. 



The arborvitae leaf-miner, R. thujaella, is one that works 

 in leaf-sprays (see pi. 2, fig. 5). It lays its eggs in a depres- 

 sion between two of the close-laid scale-like leaves. The 

 larva on hatching crawls under the edge, and in the axil 

 begins eating its way into the leaf. When it has eaten the 

 mesophyll of one leaf, it enters another either through the 

 base or through overlapping surfaces, without coming out 

 into the open. Thus it extends its operations until a con- 

 siderable portion of the spray is hollowed out, and appears 

 transparent when held up to the light. The species hiber- 

 nates as a larva, and pupation occurs in the mine. A good 

 account of the species is given by Britton and Zappe (1922) 

 with figures and bibliography. 



The Ceanothus miner, R. Ceanothiella of the mountain 

 region of central California, is a deciduous shrub-miner 

 whose work has been briefly described by Miss Braun (1921) 

 as follows: 



The mine starts on the lower side of the leaf, usually next the 

 midrib; the entrance guarded by a short tube of silk. The mine 

 is at first linear, with branches extending out from it, later, blotch- 

 like, including the linear portion. Pupa in a cocoon between two 

 leaves tightly spun together. 



Nealyda 



This genus includes a few southern and western species 

 whose larvae are considerably flattened and whose pupae are 

 formed outside the mine on a leaf in dense oval, flattened, 

 white cocoons, from which the pupal skin is not protruded 

 on emergence of the adult. The egg is laid on the upper 

 side of the leaf. The mine is more or less trumpet form or 

 blotched, having something of the appearance of Lithocolle- 

 tis, as does also the flat larva, if one disregard legs and 

 mouth parts. Two species from Florida and one from Colo- 



