72 



INSECTS. 



infected fruit drops to the ground, and the larvae when mature pass out to become 

 pupee beneath the earth. Besides oranges and other acid fruits, peaches and 

 melons are attacked by this fly. The annexed figure represents another of these 

 injurious little insects (Chlorops tceniopus), a shining yellow fly variegated with 



black bands. This species and its allies, which are most 

 destructive in the larval stage to cereals and grass, 

 much resemble in the cycle of their development the 

 above-mentioned Hessian fly. Allied to the preceding in 

 structure and habits are the members of the sub-family 

 Ortalince, containing the genus Ortalis and others. A 

 curious representative from the Malay Archipelago, 

 known as the staghorn-fly {Elaphomyia), takes its name 

 from the development of the sides of the head into 

 large branching horns. This, however, is only a sexual character, and confined to 

 the male. Finally, the small black fly (Piophila casei), known in the grub-stage 

 as the cheese-hopper, belongs to that group of Muscidce in which there are no 

 scales to cover the balancers. 



Chlorops tceniopus, with figure 

 showing side view of head 

 (much enlarged). 



Gad-Flies and Bot-Flies, — Family (Estrid^:. 



The flies of this family are mostly of large size, and many present superficial 

 resemblance to various kinds of bees. In structural characters they are nearly 

 allied to house-flies, but the head is larger and broader and the mouth-parts are 

 reduced. In the larval stage gad-flies infest, either 

 as internal or external parasites, various mammals, 

 but since those that attack domestic cattle have 

 been more thoroughly studied than the others, 

 attention will mainly be directed to three of the 

 best known forms, namely, those that infest respect- 

 ively horses, oxen, and sheep. The horse bot-fly 

 (Gastrophilus equi), which resembles the honey- 

 bee in size, colour, and form, lays its eggs on the 

 skin of horses, asses, and mules, which seem to 

 have an instinctive dread of the insect. It has 

 been noticed, moreover, that the gad-fly instinctively 

 selects for the purpose a spot that is well within 

 reach of the quadruped's mouth. The reason for 

 this, although not at first very obvious, becomes 

 clear when it is understood that the larval fly can 

 only obtain its proper nourishment in the alimentary 

 canal of its host. As soon as the maggot emerges 

 from the egg it starts to irritate the horse's skin. 

 Thereupon the horse, to remove the irritation, licks 

 the infested spot and swallows the maggots, which 

 then attach themselves by means of their hook-like 

 mandibles to the inner wall of the stomach or 



DEVELOPMENT OF HORSE BOT-FLY. 



a, Adult fly ; b, Egg attached to a hair ; 

 c, Mature larva ; cl, Newly-hatched 

 larva ; e, Pupa. (All enlarged.) 



