H YMEN OP TER A. 629 
side to the cup-like scale covering the base of the fore 
wing; the wings have no closed cells; and the ovipositor is 
usually hidden, issuing before the apex of the abdomen. 
Figures 759 and 760 represent Chalcis-fiies greatly enlarged. 
It is to this family that the great majority of the para¬ 
sites of the smaller insects belong. Thus scale-bugs are 
preyed upon by many species of Chalcis-flies. But Chalcis- 
flies also attack large insects, for many caterpillars are de¬ 
stroyed by them. The most efficient parasite of the cab¬ 
bage-butterfly is a Chalcis-fly, Pteromalus puparum (Pte- 
rom'a-lus pu-pa'rum). In the case of these larger insects 
hundreds of Chalcis-flies may reach maturity within a single 
individual. 
The larvae of Chalcis-flies usually feed within their vic¬ 
tims, but a few live attached externally. Some Chalcis- 
flies, like the members of the next family, are egg-parasites, 
and certain others are developed within the galls produced 
by members of other families (Cynipidae and Cecidomyidas), 
and are doubtless merely inquilines, instead of parasites. 
The members of one subfamily closely approach the 
gall-flies (Cynipidae) in structure and in habits. One of 
these, the Joint-worm, Isosoma hordei (Is-o-so'ma hor'de-i), 
is a well-known pest, which infests the stalks of growing 
grain. It causes a woody growth, which fills up the cavity 
of the stalk, and sometimes also causes a joint to swell and 
the stalk to bend and lop down. The presence of this insect 
is often indicated by pieces of hardened straw coming from 
the threshing-machine with the grain. There is but a single 
generation of the joint-worm in a year. The insects remain 
in the straw during the winter, the adults emerging in the 
spring. Obviously the best way to destroy this pest is to 
burn the infested straw before the insects emerge. 
The Chalcis-flies of the genus Leucospis (Leu-cos'pis) are 
very remarkable in form. They agree with the true wasps, and 
differ from all other Hymenoptera in having the fore wings 
folded like a fan when at rest. They are also peculiar in 
