THE CANADIAN ENTOMOLOGIST 249 



GALLS FOUND IN THE VICINITY OF TORONTO.— No. 4. 



BY DR. WILLIAM BRODIE, TORONTO. 



RhabdopJiaga strobiloides, Walsh ; Cecidomyia strobiloides, O. S. 



. This is a common willow gall in the vicinity of Toronto, restricted 

 to Salix humilis ; the galls are very uniform in size and form, usually top- 

 shaped, some, inclining to spherical, a little oblate below and prolate above, 

 and as the female oviposits but one egg in the terminal bud of the willow 

 shoot, the galls are terminal and monothalamous. 



The gall is a rather tightly and regularly arranged mass of from 70 to 

 80 aborted leaves, representing perhaps about 1 m. of the leafage of a 

 normal branch. 



This has been called the " pine-cone-like-gall" ; there may be a sug- 

 gestion of a resemblance to cones of Pinus reshwsa, but not to cones of 

 P. strobus. 



From December 4, 18S3, to March 21, 1898, nine annual collections 

 of galls were made, all in the vicinity of Toronto, in all about 1,000 

 specimens. The average measurement of 200 galls was 12 mm. x 15 

 mm., and the length of the deformed part of the branch, included in the 

 gall, around which the aborted leaves were packed, was 6 mm. 



The larv?e occupy cells central in the galls, formed by the folding of 

 aborted leaves; they are tightly wrapped up in these, head downwards, 

 and no doubt the irritation from the activity of feeding by gnawing the 

 growing end of the twig causes the aborting of the leaves and the develop- 

 ment of the gall. 



The larva? mature in the fall and are about 6 mm. long, of a straw 

 colour inclining to orange. They pupate early in the spring or late in the 

 fall, and the pupa? are closely wrapped up in fragile silken cocoons. 



The imagoes usually emerge during the first week in May ; it may be 

 occasionally that the larva; emerge from the gall in the fall, hibernate 

 among leaves or other rubbish on the ground, and pupate in the spring ; 

 anyway, in two cases, when I had collected the galls early in the fall, I 

 found living mature larvse on the bottom of the jar. 



Although the date of emergence of the imago is usually early in May, 

 I found it range from April 4 to May 15. No doubt the date depends on 

 the temperature of the season. When the temperature is warm the 



August, 1909 



