THE INSECT WORLD. 



353 



form of the disease known as "staggers," which is sometimes 

 extremely destructive to herds. 



From this description of the Hfe histories, so briefly given, it 

 appears that our efforts to avoid injury must follow in the direc- 

 tion of prevention. As against the species that must first be 

 taken into the mouth, the mechanical ways of preventing a 

 horse or an ox from licking any part of the body will prove suffi- 

 cient ; or frequent brush- 

 ing will at least moderate Fig. 409- 

 the injury. 



In the case of the 

 sheep-bot the matter is 

 more difficult, because the 

 flies are very persistent, 

 and encircle the animals 

 until they get an oppor- 

 tunity to dart to the nos- 

 tril and deposit upon it 

 an &^^ just ready to 

 hatch, or already hatched, 

 so that either immedi- 

 ately or in a very short 

 time the maggot makes 



its way up along the mucous membrane as fir as the passages 

 allow it to extend. All sorts of devices have been adojited to 

 prevent this, but none are entirely satisfactory. T.;r has been 

 used as a repellent, smeared on the nose, and with more or less 

 success. It is probable that fish oil and oil of tar, or carbolic 

 acid, would answer the same purpose. Powdered tobacco, used 

 to induce the sheep to sneeze and thus dislodge any maggots 

 that had already made their way in, has also been more or less 

 satisfactory. In the case of recently infested animals, a brush 

 dipped in turpentine and carefully used in the nostrils, so as to 

 reach attached larvae and kill them, is sometimes found useful. 



The family Muscidce is the largest in number of genera and 

 species in the order as well as the most difficult to classify. The 

 common "house-fly," the " blue-bottle," and the "flesh-fly" 

 are examples, and may be considered as typical forms, which 

 most of the species resemble ; not necessarily in color or mark- 



23 



The sheep-bot, QLstius ovis. 



flies ; 3, pupa ; 



4, 5, full-grown larva ; 6, young larva. 



