INSECTS AFFECTING PARK AND WOODLAND TREES 



627 



bursts, and small round granules, the size of a pinhead, protrude from the 

 openings. These grow more and more, resembling miniature clusters of 

 grapes, at which time they begin to press on each other. They are from 

 to y 2 inch in diameter, and the outer surface is covered with fine short hairs 

 which become rubbed off from the more exposed portions. The larva lies 

 in a small oval cavity at the base of each gall or lobe, and on account of the 

 tough, whitish leathery walls, there is considerable resemblance to a seed. 



Dr Fitch states that most of the galls are perforated before winter, 



indicating that the flies appear before cold weather. He adds that some 



clusters may be found in winter containing insects, and these latter appear 



the following June. 



Warty oak leaf gall. Cccidomyia pilulac Osten Sacken. Somewhat 

 rounded, hard, woody galls occur commonly on the leaves of pin, red, 

 black-jack and scrub oaks. They appear in May and become fully devel- 

 oped in August or September, at which time they are bright red or reddish 

 brown. These galls vary greatly in size and may be recognized by the 

 characteristic reticulate markings [pi. 1, fig. 16]. 



Oak hedgehog gall. ^Lcraspis erinacei Walsh. A rounded, oblong or 

 oval gall covered with numerous rather long spines, is attached to the 

 upper side of the principal veins of white oak leaves. This yellowish or 

 greenish gall with bright red spines -is rather common. 



Spiny oak gall. Cynips prinoides Beut. This globular gall about yi 

 inch in diameter, covered with numerous conelike projections, occurs on 

 the upper side of the leaves of dwarf chestnut oak. It is green tinged with 

 red and contains only one cell. 



Oak leaf seed gall. Cynips dccidua Bass. Clusters of seedlike bodies 

 often 30 or 40 together, grow from the underside of the mid vein of leaves 

 of the red oak. The larger cell's are smooth, greenish white with the apex 

 enlarged and are about the size of grains of wheat. 



Oak button gall. Neurotcrus umbilicatus Bass. This small, round, 

 brown, buttonlike gall occurs in considerable numbers on the underside of 

 swamp white oak leaves. The galls are about 1 IO inch in diameter and are 

 rather common. 



Marginal fold gall. Cccidomyia crnbesccns O. S. This peculiar 

 pocket-shaped, marginal gall [pi. 1, fig. 18] occurring in the angles of oak 

 leaves, is somewhat abundant in early summer on certain species of oak, 

 though rarely injurious. 



Oak flower gall. Andricus pulchra Bass. The rounded, shotlikc, 

 greenish white, soft, spongy polythalamous galls of this species were taken 

 on catkins of red oak at Poughkeepsie May 20, 1903, adults appeariiu 1 ; 



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