Deceubeb, 1903.] 



KNOWLEDGE. 



285 



wing fly, Chri/sopa vulf/aris. They are hollow, and inside, the 

 maxillas, (inner jaws) are fitted. Attached to the base of the 

 maxilla; are powerful tendons, by means of which they are 

 worked in and out of the mandible. So the larva is able to 

 seize prey with the mandibles, and, still holding it, to jiierce the 

 skin with the serrated points of the maxilliE, and suck its fluids, 

 an economy of means not often founi iu Nature. These larvaj 

 are highly beneficial to our gardens, as they attack the Aphides. 

 Their voracity is out of all proportion to their minute size, and 

 has earned them the name of the " Aphis Lion.'' The eggs are 

 curious ; they are placed at the end of long stalks, and a number 

 beiug always laid together, look like a little clump of fungus, and 

 are easily identified. 



Hairs on the Fore-lec; op the Fly, Empis tesnelata. — 

 The hairs of insects modify into extraordinary shapes and forms. 

 1. 



1. — Gizzard ot Earwip;, Forjirula auricularia. 2. — Ovipositor of 

 the Fly, I hi/tomiiza Jtaoa. 3.— Mandible of the ".\phis Lion," (larva 

 of Chrxisopa oulijaris'^j showing the maxilliL' enclosed. 4. — Femur of 

 the fore-leg of the Fly, Hinjiis tesselata, showing the modified hairs 

 used in holding prey. 



In some of the aquatic Heraiptera they are seen as delicate 

 filamentous veils, which hold the water and assist in the 

 propulsion of the insect. In Tiptera they have also very various 

 and remarkable developments. We find them modified into 

 hooks of an extraordinary multiplicity of shapes, and scattered 

 all over the body of the insect, teeth, brushes, and, in Empia 

 Irsneldta, into knife-blades, which, fixed into the femora of the 

 fore-legs, enable the insect to securely hold its prey. In many 

 species of flies the stronger hairs have a longitudinal striation. 

 In these knife-blades the hair has flatteneil out, but the original 

 striation remains. It is obvious that /■-'. te-'i-o-hila is predaceous, 

 and has strong piercing lancets, as well as a well-developed 

 suctorial organ in the mouth parts. 



A LiviXG Fl.Y IN THE AcT OF Feedini;. — The method 

 originated by the late Mr. R. Macer, for showing under the 

 microscope a living fly, or similar insect, while feeding, is 

 comparatively litlle known. It is very simple, always creates 

 interest, and brings to view, in a manner which is otherwise 

 impossililo of appreciation, the mechanism of the proboscis. 



The following are the necessary items for arranging the 

 exhibit : — 



1. Cones. 



2. Forceps. 



3. Glass bottle and tube. 



1. The Cone. — Small cones, about 1^ in. diameter and about 1 J in. 

 high, are made of paper and firmly cemented, the tops are then 

 cut off, leaving the apertures of varying diameter from ^^ in. to 

 I in. to suit different sized insects ; the intei-.or of the cone is 

 dull blackened. These cones have subsequently to be gripped 

 by forceps, and so that they may not slip, a narrow rim of 

 either string or paper has to be cemented round them a short 

 distance from the apex. 



2. Forceps. — Two pairs are required, one to hold the cone 

 and the other to carry a piece of blackened cardboard on which 

 honey should be placed. Both of these forceps should be 

 of the "stage"pattern, the formerhavingattheend of thejawsa 

 circular ring in which the cone is placed ; the latter have the 

 jaws mounted on a spring, so that a screw, which is carried on 

 a bridge above, can be made to press on the jaws, and so cause 

 them to recede or be brought nearer the desired object. 



3. A Glass Bottle <i,nd Tube. — The former is to contain the 

 fly, and may be of any ordinary variety; the latter is a plain 

 glass tube having both ends free and fitted with corks. 



Process of ExliJhiting. — One of the corks is removed from 

 the tube, which is then placed over the bottle in which the fly is 

 contained, the cork of that also being removed; when the fly has 

 entered the tube one of the cones is quickly placed over the free 

 end, after which the cork at the other end is removed. A small 

 plug of cotton wool is then inserted, and is gradually pushed 

 upwards through the tube into the cone, the small opening of 

 which is held towards the light so that the fly may put his head 

 through. When it has arrived at this position the plug of cotton 

 wool is carefully placed behind it. 



The cone is now ready to go into the round-ended forceps, 

 which are fixed on the stage in the usual manner. The other 

 forceps carrying the cardboard with honey are placed in position 

 on the other side of the stage, and the bait is placed quite 

 closely to the fly's head. A 1 \ in. objective is then focussed, and 

 the honey can be altered iu position the desired amount, by 

 means of the adjusting screw before referred to, until the 

 proboscis is well displayed. 



The best form of illumination is with a bull's-eye condenser 

 and a parabolic side silver reflector. 



A Useful Dryino Oven. — Working microscopists often find 

 a dilHculty in ])roviding a suitable place for unfinished slides, 

 where dust cannot reach them, and iu knowing how to dry them 

 quickly and safely, more especially where space is limited and 

 no suitable oven available. 



Mr. L. Sandall, k.r.m.s., suggests the following method of 

 making a small oven which will be found to answer the 

 requirements of the average worker : — 



Obtain a tin about 9 in. by 8A in. by 9 in., such as a 7 lb. size 

 biscuit tin. It should be free from dents, and will need 

 thoroughly cleaning with hot soda water and properly drying. 

 It will require added to it four legs, preferably | in. thick and 

 () in. long, and half way down the interior, on eitlier side, two 

 strips of tin about 1 in. wide should be soldered and bent at 

 right angles to form brackets, on which a piece of |>lute or 

 window glass cut to the proper size could rest, and form a shelf 

 to put the slides on. 



In addition, a hole should be made at either corner on the 

 top of it about 1 in. diameter, which c;in be plugged with a 

 tightly-fitting cork, through which a thermometer can be passed 

 to register tlie inside temperature. These little extra fittings 

 will be made by any local tinsmith at very small expense. 



It will be obvious that when completed the lid of the tin will 

 not be uppermost, but when mounted on the legs will be at the 

 front to form a door. 



To give a finished appearance to this contrivance, the tin 

 work may be cleaned and enamelled with Brunswick black. 



The heating will be obtjiined by mounting a spirit or small 

 paraffin lamp on blocks of wood of suitable sjze to maintain 

 the temperature that is required. 



Those who may prefer to be able to see into the tin siiould 

 have the centre of the lid cut out and a square jiiece of window 

 glass inserted, secured by strips of tin soldered round the 

 inside. 



Waterproof Cement for Glass. — Many attempts have 

 been made to ]>rodnce a cement suitable for microscopists' use, 

 for making and repairing troughs, aquaria, etc., that will hold 

 water without leaking, and be unalVected by water. The two 



