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. 

 Svricidee. 



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. 

 Chalcidoidea. 

 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. 



