LEAFLETS FOR FARMERS, NO. 20.

New Zealand Mail, Issue 1204, 29 March 1895, Page 7

LEAFLETS FOR FARMERS, NO. 20.

New Zealand Department of Agriculture. John D. Hitchie, Secretary. OX-WARBLE, OX BOT-FLY, GAD-FLY {Hypoderma bovis). By T. W. Kirk, F.L.S., &c, London. Luckily this insect has not, so far as is known, appeared in New Zealand yet, but one or two cases have been discovered in Australia in cattle recently imported from England. United action has been taken by the various Chief Inspectors of Stock in the Australasion Colonies to urge upon the Agents-General the necessity for instructing the veterinary officers whose duty it is to pass all cattle for these colonies to make special examination in order to ascertain if any of them are. infected. All animals are also carefully watched while in quarantine, but it is difficult to detect the presence of the grub iri the early stages, and it is therefore thought desirable to publish drawings and descriptions, in order that settlers may become familiar with the appearance of the insect, and so, being forewarned, forearmed. In order to understand the loss which would follow the introduction of this terrible pest it is necessary to give briefly the life history, as observed in the United Kingdom. The eggs are usually laid during the months of June, July and August. The female fly, which is provided with a very strong ovipositor, selects, if possible, a young beast, and, alighting on the back near the spine, manages to pierce the skin and deposit a single oval egg in the hole. This operation is repeated till* all her eggs are laid. After a time the eggs hatch, and tiny, worm-like maggots emerge. The gradual growth and movements of the grub cause inflammation, and produce " tumours " or warbles. The scrubs are found within these warbles, head down, the tail, provided with breathing-tube?, being pressed against the opening. Approaching the last stage (Fig. 3), they press constantly against the openings, which are thus enlarged sufficiently to allow the exit of the grubs. These fall to the ground, where, like the maggots of the horsebot, they wriggle into the earth, or under any available shelter, and pass into the chrysalis stage (Fig. 4), from which within a month the perfect flies (Fig. 5) emerge. The fly has but two wings. The head and front part of the body are yellowish, the back portions of the body black; the abdomen is banded white, black, and yellowish. One specimen in my possession measures just three-quarters of an inch in length. It will be seen that not only does this fly ruin the hide, but it also injures the health of the beast, and causes it to lose condition. A correspondent states that the annual loss in the ; United Kingdom from this cause alone amounts to several millions sterling. At Home it is a common practice to squeeze out the grub from the cows' backs, and. to apply various compounds of tar and sulphur as preventives: but this can only be done where the herds are limited. Should the pest ever arrive in this country some other means of preventing the attack will J

have to be resorted to, and no better or easier plan could be devised than that recommended for protecting horses from the horse-bot namely, yarding the animals and spraying them with carbolic mixture. No fly will touch them while the effects last.