HYMENOPTERA 161 



Chalcis-flies in plants often produce swellings and ab- 

 normal growths called galls, but these are not to be con- 

 fused with the true Cynipid galls. 



TABLE FOR THE DETERMINATION OF THE MORE IMPOR 

 TANT GROUPS OF 



HYMENOPTERA. 



A. Abdomen of female provided with an organ for boring or 

 sawing. Trochanters of the hind legs with two segments. 

 Sub-order Terebrantia. 



B. Abdomen not at all or slightly constricted where it 

 joins the thorax. 



C. Abdomen of female furnished with a prominent 

 boring organ. Mostly larger species. Horn-tails. 

 Siriddce. 



CC. Abdomen of females furnished with less prominent 

 sawing organ. Usually smaller. Saw-flies. Ten- 

 thredinidce. 

 BB. Abdomen constricted at the union with the thorax. 



C. Wings almost entirely without veins in many species. 

 Size small, colors often metallic; abdomen short. 

 Chakidoidea. 

 CC. Wings with more distinct venation. Size variable. 



D. Abdomen very much compressed laterally seg- 

 ments usually appearing as if telescoped to- 

 gether. Gall-flies. Cynipidce. 

 DD. Abdomens more slender; fore wings without a 



stigma.* Ichneumonoidea. 



AA. Trochanters of the hind legs consisting of a single segment. 

 Females often with a stinging organ. 



B. With what appears to be a knot or hump on the peti- 

 ole or stem connecting the thorax and the abdomen. 

 True Ants. Formicoidea. 



*See Fig. 117. 



