482 



The Warble Flv. 



[NOV., 



The Landes-Okonomie-Kollegium, which is an advisory body 



composed of members of the Prussian Agricultural Chambers 



and members nominated by the Prussian 



The Warble Fly Minister of Agriculture, held a meeting in 

 ( Hypoaerma bovis ) 

 in Germany. February of the present year,* at which 



Professor Ostertag dealt with the subject of 



warble flies, and proposed that the Landes-Okonomie-Kollegium 



should support a resolution that the passing of a law in relation 



to combating the warble fly was not considered advisable. 



Professor Ostertag then passed in review the life-history of the 



warble fly and the estimated extent of the damage due to its 



depredations. The fly, he remarked, appears from June to 



September, but does not enter the cowsheds. From the time of 



Virgil it has been stated that when the females swarm and 



hum round cattle, the latter will become wild and rush about 



with tail elevated ; entering water, if near, to get rid of their 



instinctively recognized enemy. It is pointed out, however, 



that this appearance is not due to the warble fly, but to stabbing 



insects which make painful punctures. It has also been believed 



that the warble fly pierced the hide of the cattle in order there 



to deposit her eggs. But it has been shown that it does not 



attempt to pierce the hide, but with the help of an egg-laying 



tube or ovipositor attaches its eggs to the hairs. The larvae 



from these eggs endeavour to reach the mouth of the animal, 



in order to complete in the body a life-history, which has many 



interesting features. In the first place they seek the oesophagus, 



where they remain and grow for three months ; they then creep 



into the neural canal, and remain another three months, at the 



end of which, towards spring, they begin to appear under the 



skin of the animal. Under the hide the larvae, which are about 



28 mm. long and from 12 to 15 mm, broad, produce the so-called 



warbles, from which they emerge by boring through the hide 



pupating, and finally becoming flies. 



The harm occasioned by the warble fly can be gathered 



from its life-history, though it is questionable whether much 



injury is done to the grazing stock. On the other hand, the 



value of the meat is diminished by the wandering of the larvae 



* Landzvirtschaftliche Jahrbiicher : Zeitschiift -Jiir Wissenschaftlicht Landwirt- 

 schaft, tmd Archiv des Kdniglich Pixitssischen Landes-Okoiiomie- Kollegiums ^ XXXV. 

 Band. Ers'dnztm^sband I. 



