June, 1922.] Leiby: Biology OF Gnorimoschema. 91 



happen to enter the bud of the same stem and two galls are thereupon 

 produced on such a rod. 



After the larva has fed for ten days or so in the gall, it packs the 

 accumulated excrement mixed with a little silk in the apex of the 

 chamber and thus seals its entrance passageway. Subsequent excre- 

 ment is similarly packed in the base of the gall chamber, the inside 

 being always kept scrupulously clean. 



When the larva is about three fourths grown it begins to eat a 

 small channel toward the outside of the gall at the anterior end (Plate 

 VIII, Figs. 4 and 6) which is continued until the very outside layer 

 of the stem is reached. Later the outside layer is cut and used, 

 together with silk secreted by the larva, to form a peculiar circular 

 plug (Plate VIII, Fig. 3) measuring 2 mm. in diameter and 1.6 mm. 

 thick, which is so constructed and placed that it can readily be 

 pushed outward from within but not inward from without. This 

 serves as an exit hole for the adult. 



The larva ceases to feed to any extent about July 20 at which time 

 it measures around 14 mm. in length. For a period of a week to ten 

 days it lies semiquiescent within the gall, but during this time it cleans 

 out the gall thoroughly, packing all excrement in the base, and then 

 lines the gall with a thin layer of silk. Following this it pupates, the 

 last larval skin sometimes remaining attached to the caudal end of 

 the pupa (Plate VIII, Fig. 6). 



The pupal stage covers a period of about one month at Ithaca, N. 

 Y. (August 5 to September 10). 



The moth upon emerging from the pupal shell crawls to the apex 

 of the gall, and remains there until the wings are completely developed 

 and dried. It then approaches the plug of the exit hole, exudes a droD 

 of secretion which allows the ^lug to be readily pushed aside, and 

 emerges from the gall. 



Seasonal Occurrence: The writer has been privileged to determine 

 the time of appearance of the various stages in three widely separated 

 regions, viz., Williamsville, Vermont,^ Ithaca, New York, and Ral- 

 eigh, North Carolina. The insect is single brooded in each region and 



1 Many thanks and appreciation are due Mr. S. A. Merrifield, of Williams- 

 ville, Vermont, who frequently sent me galls of this species and made some 

 biological observations in this locality which have been used in this paper. 



