71 



ExODONTES. — 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- 

 iinse, 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. 



Fig. 37. Chalcidid.e. — Here we have an- 



other very extensive family ; the species 

 differing gi*eatly 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 affinis 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. 



f 



Fig. 



Fig. 38. 



Smicra and Chalchis contain species remarkable for the development of the 

 hind legs. Fig. 38 shows Smicra marice, which is a parasite of the Cecropia 

 caterpillar, and Fig. 39 gives Ohalcis flavi/pes which attacks the larva of the 

 cotton moth. 



