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OAK GALLS AND GALL INSECTS 



There are also insects of various orders which feed upon the 

 substance of the larger galls such as Biorhiza terminalis. They 

 are known as "commensals." 



On account of the number of parasites, inquilines, etc., 

 found in oak galls, it is important to differentiate between them 

 and the true gall-makers : — 



Fig. 



Wing of a Chalcid. 



Characters of the Chalcididac. Wings without a system of cells, having a 

 single nervure proceeding from the base near the costa to which it afterwards 

 passes after giving off a short vein more or less terminally thickened. 

 (Fig. I.) The angles of the pronotum do not extend back to the point of 

 insertion of the tront wings. Antennae elbowed, with seven to thirteen joints. 



Fig. 2 A . Wing of an Ichneumonid. 

 B. Wing of a Brachonid 



Characters of the Ichnemiionidac. Wings with a system of cells well 

 developed. The space in the front wing dividing the posterior cell from the 

 cubital cells, is separated into two portions by a transverse veinlet. (Fig. 2 A . 

 Antennae many jointed. Abdomen attached to the lower part of the medium 

 segment, 



