24 INSECT PESTS 



flowing mane and sweeping tail, which were given him for 

 the express purpose of slashing those flies, and whenever we 

 encumber him with harness we should endeavour to make 

 up for such limitations by a rubbing down with a paraffin 

 cloth and the fixing on of leafy twigs during the day 

 time to give him some chance against the gad-flies. 



The Ox Warble Fly (Ilypoderma lineata) also belongs 

 to the Diptera. Its habit is to hover about for a couple 

 of hours or so at mid-day in the hottest time of the year, 

 the flight being accompanied by an even, sustained hum- 

 ming sound. This sound has a remarkable eflect on 

 cattle, who seem to know by instinct the meaning of it, 

 and it causes them to stampede, suddenly rushing oflE 

 without any apparent object or reason, and, if they can, 

 they will take shelter or enter a stream, either of which 

 alternatives should be available, as the judgment of the 

 animal is perfectly right and the flies will not follow 

 them there. This stampeding, however, becomes a serious 

 matter with cows, either milch or in-calf, as it may cause 

 a poor yield in the one case, and loss in the other. Such 

 is the action of the adult flies : but that is by no means 

 all. This insect has a larva or " bot " which lives as an 

 internal parasite of oxen. The female fly lays her eggs 

 in summer time upon the hair, chiefly of the legs, and each 

 egg is firmly attached to the hair by means of claspers 

 and a gummy secretion. A sketch is shown of this 

 peculiar egg. It hatches in a day or two into a spiny 

 maggot, which irritates the skin so that the animal licks 

 the place and so carries the young bot into its mouth and 

 it passes down the throat, thus reaching the interior after 

 penetrating the wall of the gullet. The bot then changes 

 its skin and becomes smooth and " slithery " just Uke 

 the common maggots of "blown" meat, which are the 

 progeny of the Blue-bottle. The young bot is now able 

 to wander about among the tissues of its host, at last 

 settling just between the flesh and the hide. There it 

 moults and again becomes spiny, as shown in the sketch. 



