NATURAL HISTORY SOCIETY OF GLASGOW. 143 



tails, where the species of Dolervs are mainly to be found. The 

 mountains yield a few species, but unless one happens to 

 be on them on a very calm day, and when the insects 

 have just emerged, there is not much chance of anything 

 being found. 



Having caught the specimens, the next business is to have 

 them killed and brought home, and it is obvious that if these, 

 two processes can be combined, some trouble will be saved. This 

 I contrive to do in the following manner : — when caught, I place 

 at once the flies in a " killing bottle " formed of a wide-mouthed 

 bottle of strong glass, into which is placed half an ounce of 

 cyanide of potassium, over this is sprinkled some dry plaster of 

 Paris, and over that again a layer of wet plaster of Paris ; 

 whenever this has dried, and all superfluous moisture has been 

 wiped away, the bottle is ready for use. When properly prepared, 

 it will last for a couple of years, and this mode of killing will, I 

 think, be found one of the most convenient to use. But care 

 must be taken to keep it in the dark as much as possible, never in 

 the direct rays of the sun, or moisture will accumulate, and then 

 the insects will get spoiled. If kept quite dry it will not require 

 anything else inside, but if moist, small pieces of blotting paper, 

 or sawdust from which all fine dust has been removed, may be 

 placed in it. Furthermore, the insects must never be left beyond 

 a few hours in this bottle, or otherwise their colours are apt to 

 alter, yellow being changed to vermilion. I have never seen this 

 take place with wasps or sawflies, but it occurs very readily 

 with ichneumons, e.g., Bassus, more especially if they have only 

 recently been disclosed. And of course care must be taken that 

 the bottle will not fall into the hands of any ignorant person who 

 might injure himself with this deadly poison, although it is 

 difficult to see how this could be done unless it were used as a 

 drinking cup ! It will also be found of advantage to have a small 

 muslin bag attached to the cork of the bottle, for the purpose of 

 containing small Cynipidae, Chalcididae, etc., which are introduced 

 into the bag by means of a glass tube, or a quill inserted into the 

 cork, the quill or tube being also provided with a separate stopper. 

 By this method small insects are not so readily lost (by becoming 

 attached to the hairy bodies of bees, or otherwise damaged), nor 

 do they get wetted should the bottle contain moisture; while the 

 larger and commoner species are put into the bottle itself. By 



