153 



fitting stopper, with a layer of dry plaster of Paris to the depth of 

 half an inch ; pour in above this a layer, equal in depth, consisting of 

 crushed or powdered cyanide of potassium, mixed with rather more 

 than its bulk of dry plaster of Paris ; cover this mixture with a layer 

 of dry plaster of Paris to the depth of a quarter of an inch or so ; and 

 pour in above the whole a layer, half an inch in depth, consisting of 

 plaster of Paris mixed with water to the consistency of cream. So 

 soon as the top layer of plaster is dry the killing-bottle is ready for 

 use : the plaster, however, should be covered with several thicknesses 

 of blotting-paper, to avoid risk of injury to specimens in case the 

 surface should at any time become wet. The killing-bottle should 

 never be allowed to remain open. Should the surface of the plaster 

 become brown and lose its odour, the efficiency of the killing-bottle 

 may be restored by slightly scratching the upper layer. Prolonged 

 exposure to the fumes of cyanide is injurious to specimens, which should 

 therefore be removed from the bottle so soon as they are dead ; if the 

 killing-bottle is in proper working order it should not be necessary to 

 allow Tsetse-flies to remain in it for more than five minutes at most. 



Glass-bottomed cardboard pill-boxes (obtainable in assorted sizes, up 

 to 2J in. in diameter, packed in nests one inside another) should be 

 protected from probable deterioration during the wet season by being 

 first painted over with liquid glue, and then covered with strips of 

 jaconet, cut on the cross. 



Entomological forceps are provided with curved ends for holding 

 pins. Fine- (straight-) pointed forceps, preferably made of brass with 

 very little spring, are also useful for arranging the legs and wings of 

 Tsetse-flies when pinned. 



Needles mounted in handles may, if desired, be employed in place of 

 fine-pointed forceps. 



Entomological pins made of silver wire have the great advantage of 

 never becoming corroded, but, owing to their softness, need to be used 

 with special care ; for Tsetse-flies the most suitable sizes are " " and 

 "3," costing in each case about 8s. 6d. per 1,000. Of entomological 

 pins of the ordinary type, the most convenient sizes for pinning Tsetse- 

 flies are No. 20 (a very fine, short pin, which, to prevent it from doubling 

 up, should be held by the forceps near the point) and No. 7 (which 

 though fine is considerably stouter and also longer than No. 20, of 

 which an ounce contains about 3,750 pins). Both of these sizes, 

 costing respectively 9s. 6d. and 3s. 3d. per ounce, are obtainable to 

 order from the makers (Messrs. D. F. Tayler and Co., New Hall Works, 

 Birmingham) in ounce or quarter-ounce boxes, as preferred. 



Two or three sheets of cork-carpet or pith, about 6 in. square, are 

 useful as platforms on which to perform the operations of pinning, etc. 



As regards cork-lined entomological store-boxes, to contain specimens 

 when pinned, perhaps the most convenient size for Tsetse-flies is the 

 " postal " box measuring about 7 in. by 3| in. 



The platyscopic lens (obtainable, at a cost of about 22s., from either 

 Messrs. Charles Baker, 244, High Holborn, London, W.C.I, or John 

 Browning, 63, Strand, London, W.C.2) should have a magnifying 

 power of from six to eight diameters. 



CATCHING TSETSE-FLIES. Under this and some of the following 

 headings extracts are given from the British Museum (Natural History) 

 pamphlet " Instructions for Collectors : No. 7," to which reference has 

 already been made. 



