INSECT GALLS 



is originated by the act of ovipositing. In the case 

 of the Cynipid galls, however, it has been clearly 

 demonstrated that gall production does not commence 

 until the larvae begin to feed. 



The following is a list of some of the commoner 

 species of Zoocecidia found in this locality: 



Order ACARINA. 



A large number of the galls in this group are still 

 unclassified, but the type characters are well marked. 

 The different species constitute a clear phylogenetic 

 series from the simple erineum to the well-developed 

 pouch gall. The distinction between the different 

 members of this series is largely a difference in degree 

 rather than in kind, and seems to be explainable on 

 the assumption of a gradually increasing intensity 

 of stimulus from the lowest to the highest member 

 of the series. A simple erineum type is that found 

 on the underside of the leaves of Fagus grandifolia, 

 Ehrh., while EriopJiyes cibnormis, a pouch gall on 

 the leaves of Tilia americana, L., stands at the other 

 end of the series. As an average between these 

 extremes may be placed such a form as the " dimple " 

 gall on the leaves of Quercus macrocarpa, Michx. 



Order HEMIPTERA. 



These galls are characterized by a folding and 

 wrinkling of the leaf when they occur on that organ, 

 and in this particular resemble the types of the pre- 

 ceding section. 



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