Diptera. 



991 



aiKl in tlie esophaf^us in the like stage of ilevelopmeut. in favor of tliis view obs^er- 

 vation sliows fiirtlier tliat tliin-isliinned young cattle more frequently carry llv bites 

 than other cattle, that in man the uncovered parts of the skin mostly form the 

 dwelling places of the larvae, and finally that Brauer has observed the penetration 

 of the larva? of CEstromyia satyrus into the skin of guinea pigs and rabbits. The 

 circumstance that in autumn and at the beginning of winter larvie have not yet 

 been found under the skin might be because the discovery of the small and trans- 

 parent larva} in the subcutaneous cellular tissue presents insuperable diflSculties. 



The wandering of the larvae takes place 

 variously according to their mode of penetration 

 into the body. The swallowed larv^ bore 

 through the mucous membrane of the esophagus 

 and pharynx, and are found in great number in 

 the submucous connective tissue of the gullet 

 from the months of July to November. Thence 

 they wander along the blood vessels and nerves 

 in the direction of the spinal column, and even 

 pass through tlie openings lietween the vertebrje 

 into the spinal canal, and mostly remain there 

 in the dural fatty tissue, from the month of 

 December to March ; from January to July they 

 get nito the subcutaneous connective "tissue 

 which they may do without first entering the spinal canal. The 

 larva?, which accidentally bore through the skin a short time after the 

 eggs are deposited, penetrate into the subcutis at the point of their 

 deposition without any wandering about. After two moultings and 

 therefore three stages of development have been gone through, they 

 emerge from the swellings which they have produced, become pupa3 in 

 the ground in the course of 12 to 36 hours, and the fully developed 

 insect appears after about 30 days. 



Fig. 162. Larva of Hij- 

 poderma hoc is, on the 

 left from the back (con- 

 cave), on the right from 

 underneath (convex). 

 Natural size. 



Fig. 163. Bites of oestrus in the loin region of an o\„ 



Experiments of transmission with oestrus larvie have been carried out chiefly 

 Ijy Koorevaar, who placed larvse obtained from the spinal canal of slaughtered 

 cattle under the skin of a dog and a goat. In 14 days the dog was killed, and all 

 the larvae introduced were found to be alive, some in the subcutaneous connective 

 tissue, some between the muscles, in the abdominal cavity, in the wall of the pharynx, 

 outside of the trachea, and in the fatty tissue of the vertebral canal. In a goat 

 swellings were visible in the subcutis after 12 days. Similar experiments by Euser 

 and Jost with esoi)hageal larva3 were negative, but in two experiments by Strose 

 on a calf the results were positive; the introduced esophageal larvte became quite 

 mature in 3 to 10 weeks and were found in the subcutaneous tissue. 



