ISO INJURIOUS AND USEFUL INSECTS 



with head outstretched and tail turned over the back, seeking 

 above all things to plunge into water, whither the fly does not 

 follow them. This belief is probably due to a confusion 

 between warble-flies and gad-flies. The galloping cattle have 

 been terrified by the blood-sucking Tabanus bovinus. The 

 warble-fly possesses no instrument capable of inflicting a 

 wound. It has lately been said that the larvae reach the skin 

 of the ox in late winter, after a long course of wanderings 

 through the tissues of the host, and that the eggs are not laid in 

 or near the back, but on the legs, and especially on the feet. 

 They are said to be transferred to the mouth by licking, and 

 make their way thence to the gullet of the ox. Dr Cooper 

 Curtice* found the young larvae of the common American 

 warble {If. lineatd), which is also British, 

 in the gullet of the ox ; this was in 

 November, when there are none on the 

 back. He believes that they make their 

 way from the gullet to the back through the 

 tissues of the ox, and declares that the 

 young worms have been found near the ribs 

 and in the muscles. When they reach the 

 skin of the back, he supposes, they bore a 

 hole in it for the purpose of respiration. It 

 is only then that the skin of the larva 

 becomes conspicuously spinous as a con- 

 sequence of a moult ; in the wandering 

 larvas the skin is nearly smooth, except at 

 the two ends of the body. It is highly probable that the method 

 pursued is identical in H. bovis and H. lineata. The first out- 

 ward sign of the parasite is a small lump, due to the gorging with 

 blood of the connective tissue beneath the skin of the back. By 

 February or March the maggot has grown considerably ; it is 

 now of a brownish tint ; the cavity in which it lies is filled with 

 pus ; the passage has enlarged and the warble becomes open. 

 From this time the larva steadily enlarges ; its skin thickens and 



* See Riley, in "Insect Life," vol. iv. pp. 302-317. (1892.) The, 

 question of the route by which the larva reaches the skin of the ox is of 

 great practical importance, because it affects the place to be treated by 

 remedies. Putting aside discussions of the probability of Dr Curtice's 

 statements, any one who has opportunities of examining the carcasses of 

 oxen during the last quarter of the year would do good service by reporting 

 whether or not the statements are consistent with the facts. 



Fig. 85. — Tumour on 

 back of ox, with opening 

 by which the larva 

 escapes. After Bracy 

 Clark. 



