352 



AA^ ECONOMIC ENTOMOLOGY. 



Checking the animals up when in use accomplishes this, and a 

 spiked muzzle, so arranged as not to interfere with feeding, will 

 answer in the stable. Frequent brushing to remove the eggs is 

 useful in bot-infested regions, and lessens the number that can 

 reach the alimentary canal. 



Numerous other species occur just under the skin of the 

 animals infested, and one of the best known of these is the " ox 

 warble," Hypoderma lineata. Here also the eggs are laid on 

 the hair and are licked off in the same way ; but the larvae, instead 

 of allowing themselves to be carried into the stomach, pierce the 

 oesophagus or other portion of the alimentary canal, and work 

 their way through the muscular tissue to a point just below the 

 skin. There they fix and increase in size, causing the swelling 

 and suppuration so familiar to farmers in some localities. Of 

 course the means just mentioned for preventing the entrance of 

 stomach bots are also applicable in this case to avoid infestation. 

 Where bots are already established on an animal, the best method 

 is to incise the skin and press out the larva beneath it, or use a 

 mercurial ointment, which, penetrating into the wound, will kill 

 the larva, so that it can be readily pressed out later, or will sup- 

 purate out easily. Some species of bot-flies undoubtedly lay 

 their eggs on the skin of the animals at the points where the 

 larvae actually hatch, and the latter work their way through just 

 there and form the swelling. Sometimes special organs are 

 attacked, as in the chipmunks and squirrels, where the testes of 

 the males are selected and the creatures are actually emasculated. 

 The fly has, therefore, been called the ' ' emasculating bot, ' ' Cuter- 

 eh^a eviasadator. In rabbits a species is found close to the 

 anal opening, and in fact most animals are more or less subject 

 to bot attack. Even man is not exempt, and several cases have 

 come under my observation where flies had laid their eggs on the 

 skin and the bots had developed considerably before the charac- 

 ter of the trouble was understood. In southern countries this is 

 much more likely to occur than in the north, possibly because a 

 much greater part of the body is there habitually exposed. 



Sheep suffer from a species known as CEstrus ovis, which lays 

 its eggs on or in the nostrils. The larvae make their way through 

 the nasal passages in the mucus beneath the skin, and even into 

 the horns. They are often very troublesome, and cause one 



