414 MEDICAL ENTOMOLOGY 



and trouble. The method is especially useful for native collectors, who 

 are not required to discriminate between species. 



Many small diptera, such as Phlebotomus, Ceratopogon and Culi- 

 coides can be caught around a strong light, such as that thrown on 

 a white sheet by an acetylene bicycle lamp ; the flies can be readily 

 caught as they settle on the sheet. An electric light placed under a 

 bell jar in the open attracts small flies in large numbers. 



The killing bottle is prepared in the following way : A wide neck- 

 ed bottle with a good stopper is selected ; about a quarter of an inch 



of dry plaster of Paris is placed at the bottom, and 

 Killing Bottle * f * t A A ( 



over this a layer of powdered cyanide of potassium, or 



simply a few lumps. A layer of plaster of Paris and water of the consist- 

 ency of thick cream is then poured on the top and allowed to set. In 

 preparing the cream, always add the plaster to the water and not vice 

 versa, or it will become lumpy. When the superficial layer of 

 plaster has set, place two or three pieces of filter paper on it in order 

 to absorb the moisture. This is especially important in the tropics, 

 and neglect of this precaution will result in many of the flies becoming 

 moist and their wings will adhere to the glass. When not in use 

 the stopper should always be placed in the bottle. If the smell of the 

 cyanide becomes weak, scratching the surface of the plaster often 

 restores it. 



Flies for museum specimens should always be killed and pinned as 

 soon as possible, as if kept in the tubes they are apt to damage themselves, 

 or to foul their wings and bodies with excreta. Those in tubes may be 

 killed either by transferring them to the killing bottle, or by dropping 

 chloroform or ether on to the cotton wool which is used as a plug. 

 These fluids should on no account be dropped into the tubes, or they 

 will alter the colours of the specimens. 



The following size of pins are the most useful. No. 0, and No. 20 

 for all small species, such as Ceratopogon, Culicoides and Phlebotomus, 



etc., and for the smaller muscids. Nos. 3, 5 or 7 are 

 Pins 



best for such flies as Tabanus and Glosslna. No. 16 is 

 very useful for pinning the card or pith to which the fly is attached. 

 Very long and delicate pins are sometimes used and with them a collec- 

 tion has perhaps a better appearance, but they require very careful 

 handling, as they bend easily when thrust into the cork, and have to be 

 manipulated with forceps, grasping the pin below the specimen. The 

 pins should be lacquered, as this prevents the formation of verdigris 

 at the point where it enters and leaves the body of the fly. 



