180 BOARD OF AGRICULTURE. 



from their habit of feeding upon plant lice, are very like the hymen- 

 optera in form and coloration, having hemispherical heads, rather 

 flattened bodies, ornamented with yellow bands and spots ; they 

 hover in the hot sun over and about flowers, resting upon them to 

 feed upon their sweets. The eggs are laid among a group of plant lice, 

 which hatch out footless, eyeless, flattened grubs, having extensile 

 bodies to reach up and grasp the Aphis by Fig. 20. 



their jaws, which are peculiarly modified for 

 seizing their- prey. They do great damage 

 among these enemies of vegetation. The 

 species of Eristalis which flies abundantly 

 in May about the blossoms of gooseberries j ^^-^ \ 



and currants, live in the water during their larval state, and are 

 called rat-taile(J maggots. The abdomen of Conops is peduncu- 

 lated, whilethe thorax is globular like Eumenes, a genus of wasps. 



Empis represents a small group of species that are allied in form 

 to the Asilidse. They are active flies, and very rapacious, seizing 

 upon other insects and sucking out their juices. They often as- 

 semble in swarms. 



Dolicliopus and allies have long legs, and are generally green' 

 colored, and occur solitary in leaves or in damp situations, or in 

 numbers flying and running on the surface of pools and running 

 brooks, appearing very early in spring. 



(Entridae, (Bot-flies.) In these flies, which are of large size, the 

 mouth parts are nearly obsolete, the flies themselves having thick 

 bodies, covered thickly with hairs. The fly lays her eggs upon 

 that part of the animal from which the larvae as they hatch out 

 may find their way by some means to burrow in the back or 

 stomach of the animal which they infest. From thence, when full 

 grown, they escape and pass through their remaining changes in 

 the earth. These grubs are very thick and soft, being broad oval, 

 with rows of minute spines along the wings of the body to aid in 

 locomotion. The Horse bot-fly larva is provided with hooks which 

 are modified maxillae, to enable it to maintain its position in the 

 stomach of that animal. The Sheep bot-fly larva lives in the frontal 

 sinus ; and that of Q^nlrus bovis in the back of cattle, forming large 

 open tumors. 



Muacidae. The common house fly, the blue bottle fly, and the 

 flesh fly, at once recall the appearace of this family, one of great 

 extent, and much subdivided by entomologists. " The larvae are 



