71 
EXxopONTES.—This division is very poorly represented in Canada, or at 
least in collections. The species are 
small, but may be distinguished by an 
examination of the mouth parts ; the 
mandibles have the tips turned outward 
(as the name of division indicates), and 
cannot therefore be used for biting. 
FLEXIVENTRES.—This division con- 
tains species which differ from all the 
other braconids in having the segments 
of the abdomen freely articulated, so 
that it can be bent under the thorax. 
There is only one sub-family, the Aphid- 
iinze, and the species are very small, yet 
they are of great economic importance, 
as they are parasites of various species 
of aphides, or plant-lice. The larva 
feeds inside the aphis, which becomes 
swollen, and finally is found fixed to 
the plant on which it has been feeding, 
a mere dead shell from which the tiny 
parasitic fly has escaped. The grain 
aphis is said to be kept in check by one 
species, which alone must save an 
immense sum to our farmers. 
Fie, 37. CHaLcIDID&.—Here we have an- 
other very extensive family ; the species 
differing greatly in structure and in habits. They are always small, but 
frequently are very brilliant in appearance, glittering with bright tints and 
metallic lustres. It will only be possible to glance at a few of the forms, as the 
great diversity of structure which obtains among them, and their minuteness 
make their study and identification difficult except for one who can devote much 
time to it. The wings have scarcely any traces of venation, except the vein 
along the front edge. 
Leucospis afinis is our largest species; a black and yellow fly about one- 
fourth of an inch long, with its ovipositor curved up over the abdomen in a 
curious manner. It is frequently found on golden-rod, and is a parasite of bees. 
Fic, 38, 
Smicra and Chalchis contain species remarkable for the development of the 
hind legs. Fig. 38 shows Smicra marie, which is a parasite of the Cecropia 
caterpillar, and Fig. 39 gives Chaleis flavipes which attacks the larva of the 
cotton moth. 
