INSECTS AFFECTING PARK AND WOODLAND TREES 



629 



Hickory button gall 



— . Phylloxera fovcola Perg. 



Flattened, circular, greenish yellow or whitish galls about )4 inch in diameter, occur 

 on the under surface of hickory leaves. 



These peculiar growths [pi. 1, fig. 19] are very interesting and are 

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

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

 it may possibly be P. foveata Shimer, a form which produces galls very 

 similar 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 developed galls the upper side is either of 

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

 yellowish green ; or entirely yellowish green with only the dimple of a 

 beautiful pink color. Beneath they are uniformly 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 and paperlike and readily 

 collapse when old. All galls are perfectly smooth on both sides. 



Ocellate maple leaf gall 



Cccidomyia ocellaris Osten Sacken 



Red maple leaves are frequently thickly spotted with circular ocellate spots about yh 

 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. 1, fig. 12]. It has been recorded by Professor Corn- 

 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 of the adult 

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



