106 LEAF-MINING INSECTS 



this genus. Its mines on the upper side of the leaves of 

 poplar are quite characteristic and conspicuous. The sep- 

 arated epidermis is in a wider tract than in the other species 

 I have seen. It is shining white — by reason of the film of 

 air separating it from the parenchyma — except in a narrow 

 stripe at the center where it adheres again on account of the 

 dark-colored semi-fluid excrement which is deposited there. 



Group III. Bucculatrix. The ribbed-cocoon makers 



Mining operations of this genus are, for the most part, 

 confined to the very young larvae, which make narrow, 

 brown, gradually widening serpentine mines, and later emerge 

 and feed externally on the surface of the leaf. In this they 

 are unique among lepidopterous larvae. One of our species, 

 Bucculatrix crescentella, recently described by Miss Braun, 

 is said to do no external feeding but to emerge from the 

 mine when full-fed and to spin at once the usual type of 

 ribbed cocoon. On the other hand some species — perhaps 

 through lack of observation — are not definitely known to 

 be miners at all. Most species feed between the cuticles of 

 the leaves of their host plants until about the end of the 

 first instar. Bucculatrix ambrosiaefoliella is said by Chambers 

 to moult once in the leaf and once under a moulting cocoon 

 on the leaf before spinning the pupating cocoon. Buccula- 

 trix pomifoliella and B. thurberiella emerge from the leaf 

 before the first moult and undergo two moults in moulting 

 cocoons. 



The egg. The eggs of a few species have been observed. 

 All are deposited upon the leaves but from the available 

 descriptions they seem to bear little resemblance to one 

 another in form. Chambers describes the egg of B. am- 

 brosiaefolia as a "minute colorless globule." Those of B. 

 pomifoliella are scattered on the under surface of the leaves 

 of apple and are said to be "minute, pale green, elliptical, 

 iridescent and roughened. " Those of B. thurberiella were 



