990 Parasitic Insects. 



causing the aiiiiiials to kick and staiiii). Tlic naciaatol)ia species are 

 much smaller and found especially out in the pastures ( Ilaematobia 

 stimulans, H. ferox, etc.) ; they disturb animals when grazing. 



The tempest fly (Hydrophobia s. Anthomyia) is a small fly which, 

 on the approach of rain, flies in great numbers around the eyes and noses 

 of cattle. The tsetse fly (Glossina morsitans) resides in the swampj^ 

 regions of Africa and transmit the trvpanosomes of Nagana bv its bite 

 (Vol.1). 



c. Bot Flies (Q^strida). These large flies pass tbrougn 

 one period of their development in the bodies of animals as larvae, 

 consisting of 12 segments, and here canse more or less severe 

 disease, according as they localize in the cavities of the facial 

 bones, in the stomach, intestines or in the snbcntaneons connec- 

 tive tissue. The completely developed larvse leave the body of 

 the host and change in the earth to barrel-shaped pnpte. The 

 female of the gadfly developing from these pnpa) harasses the 

 larger animals on warm snmmer days. 



The CEstrus (Hypoderma bovis) is a black fly, 13 to 14 mm. 

 long, wdth gray head and brownish narrow wings wdiicli stand 

 out from the body. It swarms at the beginning of simnner and 

 into the autumn, more especially from June to September, but 

 produces no harassing buzzing and does not disturb the ani- 

 mal, nor does it cause them to be stampeded, as many assume. 

 This stampede is much rather caused by other insects, prin- 

 cipally by Tabanidae (Ostertag, Strose, Hoffmann). 



The development of the oestrus is not yet knoAvn in all its details, 

 although many investigators have occupied themselves with its study 

 (Brauer, Hinrichsen, Ruser, Koorevaar, Hoffmann, Ostertag, Jost, 

 Strose). The pairing of the flies takes place on high mountain tops, 

 sunny rocks, towers and other high lying places. Nothing definite is 

 knoMTi of the manner in which the eggs are deposited. Since hitherto 

 no eggs of the oestrus have been found on the animal host, the first 

 assumption would be that the female deposits her eggs on grass, and 

 that later the eggs themselves or their larva? are swallowed by the cattle 

 when grazing (Hinrichsen). But on the other hand it may easily be 

 possi])le that the a^strus deposits its eggs on the l)odies of cattle, where 

 the eggs cannot be found, being hidden in the depths of hair or because 

 the larvte, which are transparent and therefore not readily recognized, 

 are hatched in a very short time. 



The penetration of the embryos into the bodies of cattle probably 

 takes place in great part or exclusively by the digestive canal in such 

 a manner that either the eggs or the larva^ of the fly are swallowed by 

 the animal, or according to Ostertag, the larva^ reach the cavity of the 

 mouth by active wandering. Strose on the contrary considers it possible 

 that some of the larvte penetrate through the skin into the subcutis, their 

 powerful chitinous mouth apparatus rendering them quite capable of 

 doing this. 



For the correctness of the last named assumption it may he stated that wander- 

 ing larvae only rarely are found on the way between the esophagus and the sub- 

 cutis, further that the youngest larvae in the subcutis correspond morphologically to 

 the esophageal larvae and that larvae are often found simultaneously under the skin 



