SOME NOTEWORTHY FLIES AFFECTING LIVESTOCK.

New Zealand Journal of Agriculture, Volume XVIII, Issue 1, 20 January 1919, Page 10

SOME NOTEWORTHY FLIES AFFECTING LIVESTOCK.

By

DAVID MILLER,

Entomologist.

The value of a more intimate practical knowledge of noxious insects is now recognized as of considerable importance to those interested in the various branches of agriculture. As many such species have become established in this country we cannot afford to overlook their presence, particularly at the present time when the greatest efforts are required to fully develop the resources at our command.

Amongst these noxious insects are several forms of introduced twowinged flies (Diptera) which every one connected with live-stock should be capable of recognizing, although, fortunately, at the present time in New Zealand there is practically no serious loss to domestic animals through the agency of such species. However, it should not be forgotten that these flies cause considerable damage in their native homes, and may under favourable conditions resume their depredations in this country. It is also noteworthy that we have no record of any indigenous fly attacking domestic animals, a fact which may be due to the absence before the advent of the white man of any mammals suitable as hosts. Nevertheless, since there is the possibility of certain native forms developing injurious habits (as has been the case with several vegetable-feeders) a constant watch should be kept for such species amongst our live-stock.

Besides the bot-flies of the sheep and horse (Figs. 1-4), which are already well known, there are other forms which may now be given some explanation.

THE MAGGOT-FLIES.

Sheep are frequently exposed to the attack of the maggot-flies, the larvae of which destroy the wool. Of these species occurring in New Zealand, the yellow or golden-haired blow-fly (Pollenia villosa, Fig. 5) is the most noteworthy. This fly is a native of Australia, and is easily distinguished by its golden-yellow head, abdomen, and legs, the abdomen being mottled in certain lights. In size and shape, but not in colour, it resembles the ordinary bluebottles.

• When the wool is blown the larvae or maggots quickly move away from the light down toward the skin — which they may burrow so that at first the wool appears perfectly healthy, but soon becomes discoloured, and eventually putrid and offensive, when it either peels or is rubbed off by the sheep against trees or posts. At such a stage the exposed skin is frequently covered with festering sores. The maggots usually frequent soiled wool, but they may sometimes enter the vagina of ewes, and, in cases of foot-rot, often occur in the feet.' The pupae are formed in some sheltered spot upon or in the ground.

‘ Like most blow-flies, Pollenia villosa does not only breed upon the wool of sheep, but in any decaying matter (particularly animal), the wool-blowing apparently being a recent habit. In Australia this fly is a serious pest. In New Zealand, although at present not affecting wool-growing to any serious extent, it is perhaps one of the most

abundant species of flies, and is often to be found in houses, where it is well known from its obnoxious habit of blowing meat. The greenbottle-fly (Lucilia sericata) is another injurious form, although in this way it is a much more serious pest in Europe than in New Zealand, where recent observations show that greater injury is caused by the yellow blow-fly. However, since the greenbottle is more abundant- in some parts of the Dominion than in others, it is probable that where it is plentiful its larvae are of more frequent occurrence upon

sheep. On account of their somewhat- similar greenish appearance several other species of greenbottles are often confused with L. sericata, and frequently if any of the former occurred' in districts where were cases of blown wool they were immediately condemned as the culprits.

The other two species of blow-flies which should be closely observed in regard to the possible damage to wool are the European bluebottle

(CallipKora erythvocephala, Fig. 6) and ; the New. Zealand bluebottle C. quadvimaculata, Fig. 7). They are both large flies of about, equal size and very much alike in general appearance. They may be distinguished by the following comparative details : —

THE STABLE-FLIES.

Besides the foregoing species, the larvae of which are injurious, some forms of flies have harmless larvae but are blood-suckers in the mature state. The stable-flies cause considerable discomfort to animals by piercing the skin with their awl-like mouth-parts and gorging themselves upon the blood of the beast which they - attack. Not only the domestic animals but also man may be attacked. In consequence of such blood-sucking habits the stable-flies are believed to be capable of . transmitting the micro-organisms of certain diseases.

-. The common stable-fly: (Stomoxys calcitrans, Fig. 8) is well-known as a frequenter of stables and even dwellings. ’-It is of a dark-brownish colour, with four black stripes upon the thorax and a spotted abdomen ; the mouth-parts are - in the form of an awl-like proboscis (Figi-10) pro-

jecting: in front of the head when not in use and adapted for piercing and blood-sucking. The larvae live in manure or other decaying substance, but particularly in animal matter. . ■ . . -

■ This fly somewhat resembles the common house-fly (Musca domestica, Fig. io), with, which it is usually confused, but the two are quite

distinct, as will be seen if Figs. 8, 9,10, and 11 and the following table are compared.

The stable-fly is a European insect, but there are species closely allied to it in other parts of the world. The writer found large numbers of an African species in the vicinity of water at Auckland. -. ,

THE SHEEP “ TICK ” OR KED,

Another blood-sucking fly, which has lost its'wings, through disuse, is the sheep tick or ked (Melophagous ovinus, Fig. 12). The use of the term “ tick ” in connection with this fly is really a misnomer; since the true ticks belong to another division of the animal kingdom and are not insects. The principal points of difference are the following : The

false sheep-tick possesses six legs and a more or less distinct head ; while true ticks possess eight legs when mature, and no distinct head. The so-called sheep-tick measures about | in. in length, is flattened from above and below, and is of a dark-brown colour on the abdomen

but lighter on the-thorax and head. Owing to its permanent parasitic habits : its whole lifehistory being spent upon the sheep and the parasite not living long if removed from its hostthe wings have been lost through disuse, and the legs, with their claws strongly developed, are thus adapted* for clinging to the wool. The abdomen is leathery in appearance, and just before a larva is deposited is considerably distended. The proboscis, or beak, is armed with teeth at the tip, and may be entirely withdrawn when not in use. ■

Unlike most other flies the female does not . deposit eggs, but at intervals gives birth to a single larva, which is attached to the wool of

the sheep by a glutinous substance produced by the mother. This pear - shaped larva (Fig. 13), which is about | in. in length and

of a dirty-white colour, is inactive and almost

immediately becomes a pupa. The latter is

similar in form to the larva, but is dark-brown owing to the' formation of a hard shell. The mature insect escapes through the top end of the pupa, which opens like a lid.

[Drawings. and photos by the Author.

Plant-identification. — this work, as carried out . by the Biologist, an effort is made to supply information other than the mere naming of the specimens. In all cases the agricultural significance of the plants sent is of more importance than the actual names, and those submitting weed-specimens should, whenever possible, supply information regarding the distribution of the plants concerned in their districts and in what crops they are found. . . ' '

Strychnine-poisoning of Rabbits. Fields Inspector W. Wilson, Queenstown, reported as follows in December : “I carried out another poisoning operation with strychnine and oats on the Frankton Flat between 2nd and 7th instant. I started feeding on the 2nd and fed up till the 5th. Owing to rain falling on the day I should have poisoned I fed an extra day. On the 6th I laid the poisoned oats, using 3 oz. of strychnine and 40 lb. of oats. On the following day Rabbiter McNaughton and myself picked up 770 rabbits, which I consider is very satisfactory. A large percentage of the number destroyed were half-grown, rabbits ; at that age they seem to take this poison very well. In my opinion from now on until the month of May is the best time of the year to use strychnine.” ,

— European Blow-fly (Fig. 6). ■ New Zealand Blow-fly (Fig. 7). Face . . ... Distinctly orange-red Indistinctly orange-red, almost black. Thorax A single 'orange spot on each An orange spot on each side beside behind the head , An orange spot on each side behind the head, another near the abdomen ; and a third at the base of the wing. Abdomen Prussian blue with silvery reat the base of the wing. Abdomen ' Prussian blue with silvery reAltogether violet-blue. flections . Altogether violet-blue.

—- Stable-fly (Fig. 8). House-fly (Fig. 9). Mouth-parts Posterior eye-margin Fourth wing-vein . . Colour of the • abdomen Awl-like and adapted for piercing (Fig. io, a) Concave (Fig. io) Only slightly upturned toward the end (Fig. 8) Spotted (Fig. 8) ' ' .. Tube - like and adapted for sucking liquid food only (Fig. 11, a). Straight or slightly convex ' (Fig. 11). Strongly upturned at" end (Fig. 9). Without spots, but with a central blackish - brown stripe (Fig. 9).