304 ENTOMOLOGY. 



one or more drops of the fluid balsam are delivered from a glass rod 

 .at one of the sides of these covers. The balsam runs slowly under 

 by capillarity, and it drives all the air before it, the small weight of 

 the cover assisting it to spread, until the whole area is tilled. No 

 pressure is to be used, or the elastic bodies of the Aphides will change 

 shape; and besides this, the juices will be forced through the corni- 

 cles and pores. If the balsam is thick, a very gentle heat, hardly 

 exceeding that of the cheek, may be applied, but as a rule the tem- 

 perature of a room is better than that which exceeds it, The insects 

 die immediately if they are cut off from air, and in almost every 

 case their position will be good for examination. To spread the 

 wings of a small insect, the above-mentioned small dots may be 

 spread in a row. The belly of the specimen is applied to the middle 

 spot, and by a bristle one wing may be applied to the dot on the 

 one side, and the other wing to the third dot. The cover is then 

 placed as before, and when the balsam runs in it will not disturb the 

 position of the spread wings. 



"It will be noticed that very soon after live insects have been 

 mounted in a resinous substance that will not mix with water, a 

 white cloudiness forms around each specimen. This is caused by 

 the watery juices of the insect, which ' chill ' the medium and make 



it opaque. 



" This cloudiness, however, entirely disappears after perhaps a 

 month, the moisture beiug carried slowly onwards. The same is 

 to be said of stray air-bubbles. The oxygen of the air unites with 

 the balsam, and thus hardens it; but what combination is effected 

 with the nitrogen is not so clear. However, air-bubbles in balsam 

 disappear in time, provided the former is not in too hard a condition. 



" In cases where the above small pressure is undesirable, small 

 circles, cut by round punches of different sizes out of very thin sheet 

 lead, will be found more convenient to insert between the glass slip 

 and its cover than circles of card, which are sometimes recommended. 

 The thin sheet lead from the Chinese tea-chests is very suitable for 

 punching, and as it is not porous like card it yields no air-bubbles 



by heat. 



" D. Von Schlechtendal * has described a method by which it would 

 appear that all the characters of form and color (?) may be preserved 

 in Aphides and other insects. The method consists of a rapid death 

 and drying of the insect by means of a current of heated air. The 

 Aphis, previously attached to some suitable support, is suddenly and 

 momentarily subjected to the heat of a spirit or other flame, by 

 which it is immediately killed and caused to retain its natural posi- 



*Entomol. Nachrichten, iv. p. 122. 



