INSECTS AFFECTING PARK AND WOODLAND TREES 62g 



Hickory button gall 

 Phylloxera fovcola l^erg. 



Flattened, circular, greenish yellow or wliitish galls about '8 inch in diameter, occur 

 on the under surface of hickory leaves. 



These peculiar growths [pi. i, fig. 19) arc very interesting and are 



probably the work of this species, though we were imable to obtain adults. 



This species has recently been described by Mr Pergande, who states that 



it may possibly be P. f o v e a t a Shinier, a form which produces galls very 



r,imilar to this. These structures were rather abundant on hickory leaves 



at Nassau in August. They have been described by Mr Pergande as 



follows : 



In the largest and perfectly develop(;d galls the upper side is either of 

 a delicate pale reil with the dimple darker and its basal circumference 

 yellowish green ; or entirely yellowish green with onl\' the tlini|)le of a 

 beautiful jjink color. Beneath they are uniforml)- yellowish green, often 

 with a faint reddish tinge, especially toward the nipple. On the other 

 trees, most densely covered by them, they were less beautiful, with less red 

 and shallower dimples. The walls are very thin ami paperlike and readily 

 collapse when old. All galls are [lerfectly smooth on both sides. 



Ocellate maple leaf gall 

 CccidoDiyia occllaris Osten Sacken 



Red maple leaves are frequently thickly spotted with circular ocellate spots about ;'8 

 inch in diameter, the disk being yellow with the margin and central dot cherry-red. 



This peculiar affection of maple foliage is the work of a small gnat, 

 which, judging from the abundance of its work, must be numerous in the 

 vicinity of Albany [pi, i, fig. i 2J. It has been recorded by Professor Com- 

 stock as being very common at Ithaca and as occurring at Washington D. C. 



The tissue inhabited by the gall is undoubtedly rendered of little value 

 to the plant and therefore the foliage is injured to some extent. (Generally 

 speaking, this species is not injurious, and ordinarily its work may be 

 regarded as ornamental in character, since it gives a decidedly variegated 

 appearance to the foliage. There is no unquestioned record f)f the adult 

 insect having been reared. The full grown larva drops to the ground 



