THE DIPTERA OF GUERNSEY. 57 



suck the juices of flowers. In the autumn many species swarm 

 on the blossoms of the ivy. 



The Conopidce, or Wasp flies, much resemble wasps from 

 their contracted first abdominal segment. They frequent 

 flowers, the larvae being parasitic on bees. 



The CEstridce, or Bot flies, are parasitic on horses, sheep 

 and oxen. They are termed " bots " in horses, " maggot " in 

 sheep, and " warbles " in cows and oxen. The eggs of the 

 Bot fly are laid on the hair, in those parts likely to be licked 

 by the horse. The young larva readily adheres to the moist 

 surface of the tongue, and is from thence conveyed into the 

 stomach, where they feed. 



Mr. Bracey Clarke, one of the best observers of these 

 insects, says they are not injurious ; others, however, are of 

 a contrary opinion. 



The " maggot " in sheep has a still more wonderful 

 history. Its eggs are laid in the nostrils of sheep ; these, on 

 becoming larvae, penetrate into the frontal and maxillary 

 sinuses and even the horns, and feed on their secretions. 

 When full grown the larvae fall through the nostrils of the 

 sheep to the ground, and there change into the pupa state. 

 In about two months the perfect fly makes its appearance. 



The " warble fly " of the cow and oxen is far more for- 

 midable than either of those just described. Its eggs are laid 

 on the sides and backs of these animals, and the larvae result- 

 ing from them pierce through the hide, producing tumours as 

 large as pigeons' eggs. The food of the larva appears to be 

 the pus or matters surrounding it in the tumour in which it 

 exists. Having attained its full size, it presses itself against 

 the upper part of the tumour, and, by some unknown process, 

 makes a hole in the hide about the size of a pea. Through 

 this the larva wriggles itself and falls to the ground, where it 

 soon becomes a pupa. After lying on the ground some weeks 

 the perfect fly emerges. It is a large and handsomely coloured 

 species, but very difficult to obtain on account of the rapidity 

 of its flight and the difficulty of breeding it, the larva dying 

 on being removed from the animal on which it has fed. 



The Muscidce are the most numerous family of the Diptera, 

 and includes many of the most familiar insects, such as the 

 common house fly, Mnsca domestica, the flesh fly, Sarcophaga 

 carnaria, and the blow or blue-bottle fly, Musca vomitaria. 



Amongst the few remaining families may be mentioned 

 the PiopMlidcB) which contains Piophila casei, which in its 

 larval state is familiarly known as the cheese hopper or 

 jumper, from its peculiar mode of progression. 



