2o8 GEOLOGICAL SURVEY OF NEW JERSEY. 



as destnicti\e as the Lepidopterous and Hymenopterous larvae 

 already mentioned. 



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

 but they are in the minority when compared with those made 

 b\- others of the same order H)-menoptera, the Cynipidce or trne 

 o;all wasps. These ,(^alls 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 ti.ssue and with a thin ])a])er-like co\-ering. vSome 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 arc filled, in 

 the one case with a brown sjiong)' mass, in the other with thread- 

 like fibres radiating from the center in all directii.ms to the (juter 

 wall. 



On the twigs and branches the galls ma)' be also marble-like 

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

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

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



