FLIES. 



419 



FIG. 525. Erax bastard li, 

 robber fly. 



the tarsi. They are the most predaceous of all flies, and indeed, one might almost say 

 of all insects. The greater part of them rest upon the ground, and fly up when dis- 

 turbed, with a quick, buzzing sound only to alight again a short 

 distance ahead. All their food, which consists wholly of other 

 insects, is caught upon the wing ; their luckless victims when 

 once caught in their stout, strong feet, are powerless to escape. 

 They are not particular in their choice ; any insect flying by 

 them is at once pounced upon as by a hawk. Other flies and 

 Hymenoptera are usually their food, but flying beetles, especially 

 the Cicindelidas, are often caught, and they have even been 

 known to seize and carry off large dragon flies. Not only will 

 they feed upon other Asilidas, but the female frequently resents the caresses of her 

 mate by eating him up, especially if he is foolish enough to put himself in her 

 power. In an instance that the writer observed, a female seized a pair of her own 

 species, and thrusting her proboscis into the thorax of the male, carried them both off 

 together. Promachus fitchii has been known to destroy as many as one hundred and 

 forty-one honey-bees in a single day. Some species of Laphria resemble the humble- 

 bees remarkably. 



The larvee are cylindrical or depressed, with parchment-like skin, without legs, or 

 with only slight abdominal protuberances. The larvae live chiefly 

 under ground or in rotten wood, especially in places infested with 

 grubs of beetles, upon which they will feed. The young larvas will 

 bore their way completely within beetle larvae and remain enclosed 

 until they have consumed them. Many, however, are found where 

 they evidently feed upon rootlets or other vegetable substances. 

 They undergo their transformations in the ground ; the pupae have 

 the head provided with tubercles, and on the abdominal segments 

 there are also spiny protuberances and transverse rows of bristles, 

 which aid the insects to reach the surface when they are ready to 

 escape as flies. 



The small family NEMISTRINID^E includes but little more than one hundred known 

 species, of which Europe and North America have scarcely a dozen. Many of them 

 have the wing with numerous cross veins, almost reticulate in appearance, and a large 

 part have the proboscis elongate, sometimes remarkably so ; Megistorhynchus longi- 

 rostris, from Africa, although only about two-thirds of an inch in length, has a proboscis 

 nearly three inches long, which it employs in sucking the nectar from the long-tubed 

 flowers of gladioli, etc. 



The transformation of but a single species is known, recently discovered by 

 Handlirsch, in the only common European one, Hirmoneura obscura. He observed 

 the female fly depositing her eggs deeply within the burrows of Anthaxia, a small 

 wood-boring insect, in the pine rails of a fence. The eggs were found in clusters, and 

 the young larvas hatched from them differed very singularly from the larvae of a more 

 mature growth. They were more slender, and had a somewhat different arrangement 

 of the mouth parts, but they were distinguished principally by the sixth to the twelfth 

 abdominal segments each being provided with a pair of false legs, bearing a single 

 elongate hooked seta at their tips, the hooks pointing backward ; while on the thirteenth 

 segment there were two pairs of similar setae, the hooks of which, however, pointed 

 forward, thus enabling the larvae to attach themselves firmly, and to raise themselves 



FIG. 5^6. Pupa of 

 ProctacantJvas, rob- 

 ber fly. 



