22 GNATS OR MOSQUITOES — CHAPTER II the Mosquito can be driven through it into the bottle without injury. Once inside the insect is very unhkely to find its vi^ay out, and the great advantage of the appliance is that a large number of insects may be captured in it without risk of the earlier takes escaping, but one would have to get the funnel specially made.
Fig. 6. — Ficalbi's Trap Bottle, J natural size. The insects can be killed by dropping through the funnel a scrap of blotting paper saturated with dilute hydrocyanic acid, and then covering its mouth with a piece of glass. (b) By means of a net. — Bend 2 yards of stout iron wire so as to form a ring 9 in. in diameter, with a handle about 2 ft. long, formed of the two ends twisted together. The net is a bag 2 ft. deep, secured to the ring, and should be made of fine silk gauze (chiffon) ; and a strip of cloth should be wound round the twisted wire of the handle to afford a more comfortable grip.
(c) By breeding out from larvae and pupae. — The larvae are found in pools, and in domestic collections of water, and when undisturbed generally remain at the surface. Place a score or so of full-grown larvte and pupa?, in the water in which they have lived, in a tumbler, and tie over it a covering of gauze supported on a twig or piece of wire bent into an arch.
In the course of a few days the adult insects will escape from the pupae and be found in the gauze. They should not be killed for a day or two, and it is better to introduce a slice of banana into the net so as to enable them to feed, and so fill out to their full size.
"When a sufficient number of specimens have appeared
COLLECTING, PRESERVING AND APPLIANCES 23 and been pinned the remaining larvae should be preserved in a small phial, in rectified spirit, or in 4 per cent, formaline solution, and marked with a distinguishing letter or number in order to identify them with the adult pinned insect. If spirit be used it is well to place the larvae in dilute spirit for twenty-four hours, and then to change them to rectified spirit.
The appliances required for collecting are simple and inexpensive, and, as a matter of fact, are better improvised at home than obtained from a dealer's, as the articles they manufacture are, as a rule, unsuitable for such extremely delicate specimens as those of the CidicidcB, their nets in particular being rarely fit to deal with anythmg less robust than the larger Coleoptera, while their cabinets and boxes rarely have sufficient provision for storing the large amount of camphor necessary for the safety of the collection in a tropical climate, unless one is to be continually examining them and replenishing the supply.
The first step in the preservation of collected specimens is to kill the Mosquitoes, and for this the best plan is to employ a " killing bottle," which any one can easily manufacture for himself.
Those supplied by dealers are always far too large for small Diptera such as the Culicidce.
Select a wide-mouthed phial about 3^in. high by 2in. wide, fitted with either a well-fitting cork, or preferably, with a metal screw-top. Most chemists store such bottles. In the latter case the disc of cork in the top of the cap should be removed and replaced with one of thick rubber, which may be secured in position by means of ordinary bicycle tyre-repairing cement. Mix equal bulks coarsely powdered cyanide of potassium and dry plaster of Paris, and put a depth of fin. in the bottom of the bottle; dust over this a little dry plaster, and then pour over all ^in. in depth of liquid plaster of the consistence of cream — when the plaster has set the bottle is ready for use. A bottle such as this is very handy for slipping over and catching sitting Mosquitoes, as in a few seconds the insect is stupefied, and drops into the bottle uninjured by attempts
24 GNATS OR MOSQUITOES — CHAPTER II to escape. When the insect has been taken by the net the bottle is passed into it, and it is easy to shp the bottle over it as it sits on the gauze. The Mosquito should never be left in the bottle for more than 90 seconds or it will get too stiff to be conveniently set, and it should be pinned immediately.
Another very effectual killing agent is tobacco smoke, which may be applied by holding a lighted cigarette a few inches beneath the net and letting the stream of smoke play over the entangled insect — or by puffing smoke from the lips into the pill box or bottle, if it has been caught in that way.
Chloroform is useless for the purpose, as the insects recover after setting, but a scrap of blotting paper moistened with dilute hydrocyanic acid and slipped into the pill box or bottle answers very well.
Practically speaking, the only satisfactory method of preserving Mosquitoes for identification is to pin them in the method described below.
It is of course very easy to mount Mosquitoes as microscopic specimens in balsam, or to preserve them in bottles in spirit, hut such specimens are absolutely useless for identification, as their coloration depends entirely on the reflection of light from the scales with which they are clothed, and is lost if they be immersed in balsam or any other fluid ; and on this account, although additional specimens preserved in spirit are not without their uses, carefully pinned specimens are the first essential. The following requisites are required for the work. ^ (1) No. 20 Insect pins : (Obtainable from D. F. Tayler and Co., New Hall Works, Birmingham). A quarter of an ounce, costing about half a crown, will last a long time. ' To avoid the difficulty of seeing the point of the pin, with the disc already on it, Dr. Adolf-Eysell, in the Archiv. fiir Schiffs-und Tropen-Hygiene, Nov., 1900, p. 354, recommends the use of pins pointed at both ends. Such pins would have the additional advantage of enabling one to remove the insect from the disc to examine the ventral surface ; but, if adopted, it would be necessary to first puncture the disc ; as the pin would certainly bend if forced through the disc when held above the mosquito.
COLLECTING, PEESERVING AND APPLIANCES 25 (2) Card discs — cut from rather thin cardboard by means of a 16 or 20 bore gun-punch, on a thick plate of lead. (3) A small flat piece of cork, covered with white paper, on which to place the insects while pinning them. (4) Ordinary toilet pins of medium size.
(5) An insect box. — Any small wooden box, not less than l^in. deep, may be utilised for the purpose b}?^ covering the inside of the bottom with a sheet of " cork carpet," cork, or solah pith. If intended for transmission by post, they must be very strongly made, and provided this be attended to there is not the least need for enclosing them in an outer box. Those I use are made of wood at least a third of an inch thick. Their internal dimensions are 6iin. X 3in. X l^in. The two end pieces are made of hard wood, the better to hold the nails, but this would not be necessary if one could get them dovetailed together. One of these end pieces is narrower than the other so as to leave a gap of about ^in. wide between it and the top, and before nailing the latter on, a piece of muslin, about Sin. wide, is glued across this end of the box, from side to side and along the upper edge of this shorter end. In this way, after the top has been secured in its place, a sort of pocket is left between it and the muslin, the mouth of which is formed by the gap between the narrower side piece and the top ; and the inner end of the pocket is closed by placing over it a thin slip of wood, secured to the inside of the top of the box by a couple of tacks. This pocket is then filled with a mixture of camphor and naphthaline, and its mouth closed by means of a slip of wood forced into the gap, and held only by friction, so that it can be at any time readily prized out and the pocket refilled. This box portion is made to lift off the bottom, which consists of a simple piece of thin plank, on to which is tacked a piece of " cork carpet " exactly fitting the internal plan of the box. As there are no sides to get in the way, it is far easier to arrange the specimens in position than in insect boxes of the usual plan. The boxes may be made deeper, so that they can be utihsed to carry a killing bottle and other materials on the outward voyage, and some
26 GNATS OR MOSQUITOES— CHAPTER II have returned from the uttermost ends of the world simply wrapped in brown paper, and have landed their cargoes in good condition, so that the plan can be recommended as having stood the test of rough actual practice. The insects should be pinned immediately after killing, as if left for more than a few minutes they get so stiff that it is difficult to arrange them nicely in position without damaging the legs. As a rule, it will be found that they die with the wings nicely spread out at right angles with the body, so that the insect w^hen shaken out of the bottle on to the setting cork lies naturally on its back. The process of pinning is conducted as follows : — Fig. 7. — To Illustrate the Method of Pinning a Mosquito: Twice Natural Size.
(1) Take a disc and write on it date and place of collection— " House," " bites," " sylvan " — or other information ; also a distinguishing letter if there be several species. (2) Place the disc, writing upwards, on the piece of cork and then take an insect pin in a pair of forceps close to the point and transfix the disc near the middle. (3) Place the Mosquito on the cork on its back. (4) Take the pin, with the disc on it, in a pair of forceps near the head, and holding it so pass the point through the thorax of the insect between the roots of the legs from venter to dorsum.
COLLECTING, PRESERVING AND APPLIANCES 27 (5) Pass a common pin through the disc, near the edge, and force the point of this into the cork at the bottom of the box.
(6) Spread out and arrange the legs and wings in suitable position by means of a fine-handled needle. For handling the pins it is best to obtain a pair of specially-made entomological forceps, but if such be not available the "ciliary" forceps used for extracting eyelashes will serve very well.
In arranging specimens in the box for transmission by post, care should be taken to force the pins well home into the cork, and additional pins should be placed between the contiguous discs so as to prevent their shifting laterally, in the position shown in the figure.
Fig. -To Illustrate Method op aeeanging Pinned Insects FOR Transmission by Post.
a a a, pins carrying the discs ; b b b b, extra pins placed between the discs to prevent lateral movement.
Another plan is to thrust the disc pins into the cork obliquely, so that if the disc shift it will rest against the cork instead of the next specimen ; but this method is not so efficient as the first.
Insect boxes for keeping a permanent collection are best obtained from regular dealers, as they require to be nearly air tight ; but it is well to specify that they should be lined with " cork carpet," as this holds the pins much better than sheet cork, and a space ^in. wide should be partitioned off one end by a slip of wood, to contain a long narrow muslin bag full of naphthahne or camphor.
28 GNATS OR MOSQUITOES— CHAPTER II After a few trials it will be found that pinning an insect in the way above described involves far less trouble than making it into a microscopic specimen ; but if materials for pinning be wanting, fairly recognisable specimens may be made by mounting the insect dry in a deep cell, or in one of the slides recommended by the late Dr. Carpenter for mounting foraminifera .
These consist of a slip of deal 3in. X lin. X iV^-> with a hole |in. in the middle. This perforation forms the wall of the cell and is closed on both sides with ordinary cover squares, secured in place by perforated labels, so that the specimen between the covers can be viewed from either side. The sides of the perforation should be brushed with creasote to prevent mildew, and the preparation dried as rapidly as possible in the sun.
Wings mounted dry as microscopic specimens are, however, valuable, but when made, great care should be taken to mark with corresponding letters slide and pinned specimen, without which latter such slides are valueless. Specimens may also be transmitted fairly safely in short lengths of glass tubing of a size just sufficient to admit the insect, but too small for it to shake about easily. The tubes should be simply tied up in a square of muslm, as if sealed the contents are certain to mildew; but whatever plan you adopt, ON NO ACCOUNT PACK INSECTS IN COTTON WOOL, as it is impossible to extricate them from it without breaking them. Tubes may also be made by rolling a piece of gummed paper round a pencil and cutting them to suitable lengths when dry.
Just as mature insects can be obtained from larvae, so it is generally possible to get larvse from the former ; but a somewhat larger apparatus is necessary. Take an earthenware dish, at least 1ft. in diameter and 4in. deep, and fill it with puddle water which has been strained through muslin to avoid the fallacy of its already containing larvae. A cover is made for this consisting of a square of thin plank a few inches wider than the dish, with a large hole occupying the greater part of its centre. In the four corners are small holes into which are fixed four small upright sticks
COLLECTING, PRESERVING AND APPLIANCES 29 about 18in. high, so as to form the supports of a miniature Mosquito net made of gauze or the material known as " leno," which is made close by means of tin tacks to the edges of the plank.
The whole thing can be lifted off and on to the dish, and when in position a Mosquito introduced into the net is securely confined. The triangular corners of the board can be utilised to carry banana or syrup as food, or may be smeared with mud in order to ascertain if the species ever deposit eggs in such situations. It is best to experiment Fig. 9. — Apparatus for Breeding-out Insects. with females that have had a feed of blood ; or in the case of sylvan gnats with specimens taken in the open, as unless fully fed they will rarely deposit their eggs. The form of the egg boats, or groups in which the eggs are deposited, should be carefully noted and the larvae preserved when sufficiently grown.
It is rarely necessary to confine males, as most species couple immediately after escape from the pupa. The above appliance is also useful for obtaining from larvae large numbers of individuals for use in observations on malaria, filariasis, &c. A piece of cardboard is slipped under the opening so as to close it, and in this way the contained Mosquitoes can be carried without injury to the subject of experiment, and liberated under his Mosquito net by simply removing the card and inverting the net. By means of a simple apparatus of this sort the life