208 GEOLOGICAL SURVEY OF NEW JERSEY. 



as destructive as the Lepidopterous and Hymenopterous larvae 

 already mentioned. 



Galls made by saw-fly larvae have been already mentioned ; 

 but they are in the minority when compared with those made 

 by others of the same order Hymenoptera, the Cynipidte or true 

 gall wasps. These galls may appear on almost any part of the 

 tree when young ; but, when older, trunks and larger branches 

 are exempt : and they are as diverse as the places they attack. 

 Oaks are favorite subjects, but other trees are by no means 

 free from them. 



On the leaves the galls are usually more or less spherical or 

 marble-like, but they differ much in size and texture, being 

 sometimes quite solid with thick walls, sometimes filled with 



Figure 3. A spongy oak gall : from Riley. 



loose tissue and with a thin paper-like covering. Some are 

 small and some are large, but that fact does not indicate the 

 size of the larva that causes the gall. Two of the largest species 

 occurring on oak exceed an inch in diameter and are filled, in 

 the one case with a brown spongy mass, in the other with thread- 

 like fibres radiating from the center in all directions to the outer 

 wall. 



On the twigs and branches the galls may be also marble-like 

 in appearance or they may be mere swellings or other protuber- 

 ances. One of the largest and most common forms occurs as a 

 potato-like swelling on the trunks and branches of young and 



