CO885-(20-21) — Page 133

PUBLIC RECORD OFFICE

TILLTI

C.O.

Reference :-

885

20 PUBLIC RECORD OFFICE, LONDON

ALLY WITHOUT PERMISSION OF THE BE REPRODUCED PHOTOGRAPHIC- COPYRIGHT PHOTOGRAPH-NOT TO

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but, whenever possible, specimens of the damaged fruit, seeds, stems, &c, should be sent home, in order to illustrate the nature of the injury done.

ALCO SOL.-The following is a simple method of diluting alcohol (or formalin) of known per cent, to any other desired per cent. : of alcohol of known per cent. take the number of cubic centimetre a represente by the figures in the required per cent., ald enough water to bring the whole up to the number of cubic centimetres representel by the figures in the known per cent. will be of the required per cept.

The mixture Example. To make 60 per cent, alcohol from 95 per cent. alcohol, to 60 cc. of 95 per cent. alcohol add enough water to make 95 cc.; the result will be 95 cc. of 60 per cent. alcohol. Or, again, if a wine-glass be taken as the unit of measurement, a mixture of 60 glasses of the alcohol and 35 of water, or & of acoh ›l and 3 of water, will give the required strength.

In the case of insects preserved in spirits it is desirable to keep hem for a day or two in a weak solution of 35 or 40 per cent, before tran: ferring them to the final solution of 65 or 70 per cent.

Where alcohol of known strength cannot be obtained, any spirituous liquid may be used provided it possesses the requisite strength. Any spirit which takes fire immediately on the applica- tion of a light, without having been previously warmed, is strong enough to be used for the preservation of animals.

Insects intended for anotomical examination must be fixed by heat, as their chitinous envelope is penetrated so slowly by alcohol that, if this be not done, they decompose before the preservative can reach them. It is sufficient to bring them to boiling tempera- ture in a test tube of water; but for delicate histological work it is better to boil in a mixture of equal parts of 90 per cent. alcohol (ordinary rectified spirit) and an aqueous solution (1 in 500) of perchlorile of mercury. preserved by this method.

Even protozoal parasites are well When fixed, preserve in 90 per cent. alcohol. Methylated spirit should not be used, as its neidity and other impurities may lead to embarrassment in the use of aniline stains.

The corks of tubes containing alcohol should be covered with paraffin wax to prevent leakage. In hot climates the wax of a scarine candle will be found more satisfactory on account of its higher melting point.

Collectors who desire to assist the committee in furthering the organised study of African economic entomology should send their material to-

The Scientific Secretary,

Entomological Research Committee,

British Museum (Natural History),

Cromwell Road, London, S.W.

INSTRUCTIONS FOR COLLECTING LARGER DIPTERA (TWO-WINGED FLIES). COLLECTING.-In general, flies should be brought home alive in the glass-bottomed pill-boxes; but when large numbers are being caught this is sometimes impracticable and a cyanide-bottle contain- ing pieces of soft crumpled paper should be carried in the field. It is worth nothing that Diptera may often be captured in quantities

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by sweeping in open marshy ground or in damp shady places. When a good many have thus been secured in the net, it should be waved rapidly backwards and forwards with one hand, then with the other hand the bag of the net should be seized near the bottom so as to imprison the flies in a small space; this portion can then be placed bodily into the killing-bottle for a minute or so, and when the insects cease to move they can all be transferred to the bottle. The flies which are most urgently required are those which suck the blood of men and animals, and of these long series should be sent from every different locality visited. duc), the so-called "stable flies

"Iorae flies " (Tabani- (Glussina) may often be capture 1 while attacking man and other (Stomorys) and tsetse Hies mammals; and it should be remembered that freshly killed animals are often as attractive, if not more so, than living on es.

KILLING.-Flies brought home alive may be killed by any of the methods recommended for mosquitoes.

PRESERVING,— For general purposes these insects should be preserved dry, either pinned or in papers.

Pinned Specimens. For insects not larger than a blue-bottle a No. 10 pin should be used, and they should be treated in exactly the same manner as recommen led for pinned mosquitoes. In the case of larger flies, staging is unnecessary and they may be pinned with the long No. 22 pins. The insect should be pushed up the pin for at least two-thirds of its length and a card dise, on which all the data have been written, should be run up the pin close beneath the insect, so as to serve as a support for its legs.

Unpinned Specimens.—Prepare a number of rectangular pieces of fairly thin soft paper; 2 × 24 inches will be the most generally useful size, but 21 x 3 inches would be needed for the largest Diptera. Take one of these papers and write on it all the par- ticulars of capture, including the locality, date, name of collector &e. Then fold the paper along the dotted lines as shown in the diagram (Fig. 1). Place the fore-finger of the right hand into the envelope thus made (Fig 2), and with the finger and thumb of the left hand firmly twist the apex so that a rigid pocket 18 formed (Fig. 3). Place one insect in this, close the open portion by folding over the upper edge, and pass the thumb nail along this foldel elge so as to secure the insect firmly (Fig. 4). Never use gum to fa ten the edges.

PACKING, Pinned Insects.—These should be treated in precisely the same manner as recommended for mosquitoes. In the case of large insects, special care must be taken that the pins are firmly driven into the bottom of the box as far as they will this never hold the pin above the insect, but always below it.

go. In doing Insects in Papers.-For packing these, take a small tin or wooden box, pour a few drops of medical creosote into it to prevent mould, and then cover the bottom with a sheet of paper, then carefully put in the envelopes in such a way as to minimise the pressure où the insects, and replace the lid as soon as possible to prevent the evapo- ration of the creosote. When the box is full, place a layer of teased-out cotton-wool on the top of the envelopes, using just suffi- cient to prevent them from moving about without unduly pressing the specimens. Carefully pack the box in a covering box, and diswatch

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