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DIRECTIONS
YOR TIL
COLLECTION OF BLOOD-SUCKING INSECTS AND OTHER ARTHROPODS CONCERNED IN DISEASE TRANSMISSION.
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The study of disease-transmitting insects and ticks is one of considerable practical and scientific importance. It is essential to accurately determine the species of these arthropods which are concerned in the spread of disease both in man and animals. In most cases it is impossible to identify the species abroad, and even at home it is usually necessary to refer specimens for identification to experts on particular groups.
In issuing this request to medical men and economic zoologists in the various services abroad, in the tropics and colonies, the request is coupled with the offer to help those who wish their specimens identified. Collections should be accompanied with a covering letter. They will be immediately acknowledged on receipt, and the determinations of species returned to the col- lectors at as early a date as possible after specimens have been submitted to different experts.
FLIES.
Diptera or flies are distinguished in general by possessing only one pair of wings, and also by the fact that behind the wings, on the next segment, are borne small knobbed organs called "balancers." Flies may suck blood (Mosquitoes, Horse- flies, Sandflies, &c.) or be parasitic on man or animals, either in the adult or larval state (bots, &c.).
Collection. For collecting flies only a moderate outfit is needed, the necessary articles being a net, a killing bottle (failing which chloroform may be used), entomological pins, a pair of entomological forceps, boxes, and cork.
The net. For actively flying forms a net is necessary. Any If none of the ordinary butterfly nets will serve the purpose. are to hand an efficient net is easily made :-(.) Bend a stout piece of wire (telegraph wire will do) into a circle and insert the two ends into a stick. The circle should have a diameter of about one foot. To the wire attach a muslin bag, which should be about two feet in length and should taper to a blunt point, the seams being made to come on the outside in order to avoid giving lodgment for small insects. (b.) A stouter and more convenient form is made thus: Procure a Y-shaped tube, the two forks having a narrower bore than the stem, and making a right angle with each other. Fit an ordinary cane into the forks and a stout stick to serve as a handle in the stem. The cane is thus bent into a circle, to which is attached the muslin net as before, the base of the net being turned over in such a way as to form a tube through which the cane can be pushed. This makes both a cheap and portable net.
The killing bottle.-This can be made by any chemist, or a simple one may be prepared as follows. Into a wide-mouthed bottle put a half-inch layer of mixed plaster of Paris. Above this pour a layer of mixed plaster and potassium cyanide to a depth of half an incl. The cyanide may be in small lumps or powdered. Cover the whole, first with quarter of an inch of dry plaster, then with half an inch of plaster moistened to the consistency of a cream.
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