DIPTEROUS LARV.E 55 



tongue for nine daj's, during which time it grew to three times its first 

 dimensions. Before leavmg the buccal mucosa the larvae probably 

 undergo a molt and then proceed to the stomach. These observations 

 indicate that the larvae of the botfly escape from the eggs when the horse 

 bites at his skin or rubs it with his lips, and that the}' burrow into the 

 buccal mucosa where they undergo a degree of development before 

 passing to the stomach. 



Within the stomach cavity the larva fixes itself to the walls bj- its 

 buccal hooks. Later the head becomes deepl}' mserted into an alveolus 

 which is formed mider the influence of the irritation to the mucosa. In 

 this position the larva feeds upon the tissue juices and the products of 

 the irritation which it sets up, becoming fully grown in about ten months. 

 The period of larval development usually terminates from May to 

 August, more especially in June, due to the fact that the deposition of the 

 eggs occurs most actively in the month of August. At this time the 

 larva becomes detached from the gastric mucosa, passes to the intestines, 

 and with the mtestinal contents leaves the body of its host. 



The change into the pupal stage is made either in the horse manure 

 or after the larva has burrowed for a short distance into the ground. 

 At the termination of pupation, which lasts from four to six weeks, the 

 matured fly creeps out, and, after fertilization by the male, proceeds to 

 deposit ova for another generation. 



Tabular Review of Life History of Gastrophilus Intestinalis 

 L Adult Flv. — (August.) 



I 



2. Eggs . — Attached to hairs of horse (Aug. and Sept.); 



I approximately 2 weeks. 



3. Young Larvae. — Upon or within mucosa of horse's 



I mouth. 



4. Larvae (Bots). — Attached to wall of horse's stomach. 



I Stages 3 and 4 approximateh' 10 



I months. 



5. Pupae . — Free (June) ; approximately 6 weeks. 



6. Adult Fly.— (August.) 



Effect. — The degree of injury due to the presence of the larvae of 

 this botfl}' will depend upon their number and location. .That the 

 stomach may be invaded by a considerable number of bots without 

 apparent disturbance to this organ is probably due to the fact that they 

 most commonly attach to the esophageal portion, this region of the 

 horse's stomach havhig a less important part in the function of digestion 



