182 SEVENTEENTH Report STATE ENTOMOLOGIST oF MINNESOoTA—1918 
alone in the field for many years, to systematic and ecological work 
in this suborder. As far back as 1867, Kirchner listed 2,407 Euro- 
pean species, and more than 4,000 species have been described. 
There are probably more than 1,000 species in the group in 
North America and a large field is still open for investigation as to 
species both in Europe and North and South America. 
The group exhibits great variety in methods of parasitism; a large 
number live in galls, feeding on the gall makers themselves or guest 
insects frequenting the galls; others attack caterpillars; some feed only 
on pupae; others prey upon bees; some on scale insects and aphids, 
PIC IOLMTI 
1 FrKQO0OCLIT 
ie 
> 
LOIET LTT 
LOM? LMI 
) el qohLr 7 
lig. 66. Thorax of Syntomaspis, typical of the Chalcidoidea.—F rom The Hymenoptera 
of Connecticut. 
and others are found in the egg-case of cockroaches. One European 
species is parasitic on the common housefly. Other species prey upon 
the larvae of the Hessian fly. It is evident that this group is of the 
greatest economic importance. Illustrative of this fact is the condi- 
tion sometimes prevailing in the south, where in a certain year, 95 per 
cent of the eggs of the destructive cotton caterpillar were killed by a 
chalcid parasite. 
As evidence of the work of one chalcid, we may cite the case of 
Leucospis gigas, the female of which pierces the masonry-like hard- 
ened mud walls of an European mason bee. By patient work, the 
