W. St. GRAHAM — tME PHOTOGRAPHY OF DIPTERA. 155 



The Preparation op the Insects. 



Insects to be photographed are best killed in a cyanide bottle, for not being- 

 rendered so stiff as those killed by chloroform vapour, they are more readily set, 

 and require less handling. The most satisfactory preparations are those made 

 from insects mounted immediately after being killed. Fairly satisfactory prepara- 

 tions can be made from dried unmounted specimens that have been thoroughly 

 softened and relaxed by being placed upon damp sand in a closed vessel for a 

 couple of days, but they require very much more skillful treatment than do 

 freshly killed specimens. 



Take a pin of suitable size (No. 20 for small. No. 7 for large Diptera), cut off 

 the head and sharpen the cut end. Then take a suitable disc of 3-ply Bristol 

 board and push the pin through the centre of the disc. Lay the dead insect upon 

 its back upon a sheet of smooth paper and carefully insert the point of the pin 

 into the thorax in the median line vertically and in such a position between the 

 fore and mid coxae that the subsequent setting of the legs will not be obstructed. 

 The i^in is then kept perpendicular to the surface and carefully pushed into the 

 insect until it touches the chitinous covering of the upper surface of the thorax, 

 but it must not penetrate or mark this surface in any way. Care must be taken 

 to insert the pin vertically and not to move the insect about upon the paper, as 

 by so doing the surface of the thorax in contact with the paper would be denuded. 



The disc with the insect now pinned upon it is raised from the table by means 

 of the portion of the pin projecting from the cardboard, and the pin is gently 

 drawn through the disc until the legs of the insect are in contact with the card- 

 board. The nearer the insect is drawn to the disc the easier will be the 

 subsequent focussing, as the legs and body will be set more nearly in the same 

 plane and less depth of focus will be required. If drawn too close the position 

 of the legs will be unnatural and the effect bad. With each increase of 

 magnification this becomes a more important matter. 



Now lay the edge of the disc upon a sheet of cork and push a longer and 

 stouter pin through the card near its periphery. The preparation is now mounted 

 as a mosquito should be, and is fixed by meaus of the stout pin on a broad cork 

 setting-board. Some minutes after its insertion the pin in the thorax becomes 

 fixed by the drying of the exudation round it, and the further setting can be 

 proceeded with. The wings are now gently and equally extended and retained 

 in this position by being passed through loops of thick notepaper raised on pins 

 to the height of the base of the wing. The legs are placed in a natural position 

 and so as to display their distinctive marks, being retained in position by slips of 

 thick note-paper or pins ; and lastly, the position of the head and antennie is 

 corrected if necessary. The board with the insect upon it should be protected 

 against the attack of ants, &c., by being placed in a creosoted box, and should be 

 inspected daily so that readjustmeuts, rendered necessary by the drying, may be 

 effected while still possible. The insect should be allowed to dry sufficiently for 

 both wings and legs to retain their positions after the paper supports have been 

 removed. This usually requires some da^^s, but photographing should not be too 

 long delayed as the distortion and change of colour, induced by drying, may set 

 in early and damage the specimen for picture-making. 



