The Spectator., 1916-02-25

(From Weekly News Letter United States Department of Agricultural Specialists of the department are urging cattle owners, in the North as well as in the South. to take steps to rid their cattle of OK warbles or wolves" the importance of which to the cattle industry has been generally underestimated. OK warbles are the whitish grubs or maggots which de- velop from the eggs deposited by cer- tain flies known as warble flies or heel flies, and which injure the hides, reduce milk flow and retard the growth of the animals. The maggots are con- monly found just below the skin on the backs of cattle in the spring. Their presence is revealed by local swellings about the size of pigeons eggs, each with small central hole or perfora- tion through which the maggot when mature, emerges to enter the ground and change to the adult or fly stage. When full grown the grub is about three-fourths of an inch in length.
 In the past trouble from the warbles has largely been confined to cattle in the South, but recently the bureau of entomology has discovered that sec ond species, heretofore not found in this country but known to be even a more serious pest in Europe than is our native warble. has become we'll es- tablished in certain districts in the northern part of the United States While it is probable that this so-called European OK warble will not be of as great importance in'the southern part of the United States as the species al ready established, there Is every req. son to believe that unless checked 1t will become generally distributed throughout the northern half of the country. This European species Is now generally distributed throughout New York and the New England states and few specimens have been ob- tained from western Pennsylvania, western Maryland, southern Michigan, eastern Iowa and Missouri, and west ern Washington. Attention is also di rected to the fact that this species is new generally distributed throughout southern Canada. The department, therefore, Is calling attention at this time to the danger of spreading this species promiscuously about the coun- try, and is urging cattle owners to take the simple means necessary to pre- vent it's spread.
 Until recently warbles were not re- garded as serious even in the South, because it was thought that the loss they occasioned came principally from the damage they did to hides. Even this loss in the aggregate, however, is important, as hides show warble holes three to six months in the year, and for hides that show even moderate warble infestation. In many cases the sears left after the holes have healed cause buyers to cut prices consid erably.
 The loss from the warble, however, is by no means limited to the holes the maggots cut in the hides. Extensive investigations in Germany and Den- mark indicate that the losses through reduction in milk supply in dairy cat tie, the retardation of growth in young stock. and the loss of flesh in all classes of animals are twofold greater than the damage done to the hides. In some of these tests the early extrac- tion of the grubs from the backs of in- Tested cattle resulted in an increase of nearly 25 per cent in the milk produc- tion. Animals from which the grubs had been extracted showed a gain of more than five per cent in weight over similar animals in which the pests were allowed to develop normally.
 Thus far the veterinarians and en- tomologists of the department have determined no better way of control ling these pests than through the sys- tematio extraction and destruction of the grubs from the backs of infested animals.
 When the larvae are nearly ready to leave their host they may be easily squeezed out by pressing the swelling Wilu lnC hnSCiS, Dut II Apt SO lar QG- veloped it is often very difficult to get them out by squeezing. In such cases a slender pair of forceps may be used for pulling them out. If the swelling and it's opening are still very small, the best way of extracting the grub is to make an incision with knife, after which the grub can be squeezed out by applying strong pressure. Kill the grub when removed.
 It Is important that warbles be re- moved as early in their development as possible. This relieves the infested animal from the irritation and pre- vents the enlargement of the exit holes. While this practice is not ap- plicabie to ranch conditions. it Is