204 



NA TURE-STUD Y RE VIEW 



[12:5— May, 1916 



the gall-fly is named Dryophanta erinacei. This gall is rounded or 

 oblong with the surface netted with fissures, and more or less 

 densely covered with spines. It is usually attached to the midrib 

 but may also occur on the lateral veins and on either side of the 

 leaf. When young it is yellowish-green, but in autumn it becomes 

 yellowish -brown, much lighter in color than the tinting of the leaf. 

 The gall first appears late in June, and reaches full development 

 about the third week in August. 



The adult gall-flies of the autumn generation emerge from the 

 gall during the first part of November and fly to the leaf or flower 



buds of the white oak; here they 

 lay their eggs among the young 

 leaves or flowers. The eggs re- 

 main here throughout the winter 

 in a dormant condition undergo- 

 ing development in the spring. In 

 May the young larvae hatch and 

 their appearance is soon followed 

 by the growth of thin-walled galls 

 on the scales or terminal part of 

 the leaf and flower buds. Each 

 gall contains a single larva 

 bathed in a watery fluid. These 

 larva? grow very rapidly and 

 transform into adult gall-flies 

 about the end of May. The gall- 

 flies of this spring generation then 

 lay eggs in the veins of white 

 oak leaves and start the growth 

 of another set of oak hedgehog 

 galls. The life cycle of this gall- 

 fly may be written briefly as 

 follows : 



i . Adults of autumn genera- 



Oak or May Apple 



Fig. 4. 



Large, globular, more or less 

 smooth outside and filled with a 

 spongy substance, in the center 

 of which is a hard woody kernel 

 containing the larval cell. From 

 I to 2 in. in diameter. Whin 

 fresh, it is pale green, soft and 

 succulent, with the contents whit- 

 ish. Later in the season the shell 

 becomes brown, hard and brittle, 

 with the kernel woody and the 

 spongy substance dark brown, but 

 remaining soft. Confined to the 

 leaves of the trees belonging to 

 the red oak group. (After Beuten- 

 muller). 



tion emerge from oak 



hedgehog 



gall early in November. 



2. These lay eggs in leaf and flower buds of white oak. 



3. Early in May these eggs hatch and thin- walled galls are 

 formed on the scales or leaf and flower buds. 



