468 SUMMARY OF CURRENT RESEARCHES RELATING TO 



one hand and a rapid evaporation on the other. In this way small 

 insects may be sent through the post, and in a far better condition 

 than can be secured in any tin boxes, even though they be filled with 

 leaves. If a slip of some succulent leaf be rolled round each quill, to 

 retain moisture, a bundle will conveniently pass through the post. 



For preservation (other than on a slide) the best plan is to drop 

 the insects into small flattened glass tubes partially filled with a 

 suitable liquid, then draw the tube to a fine point, break the end off", 

 and warm the empty space (or, better, expel the air by a pump), and 

 the tube can be entirely filled with liquid, and then sealed with the 

 blowpipe. 



For mounting microscopically, five or a dozen spots of fluid 

 Canada balsam should be dotted on a slide from the head of a pin, 

 and by means of a hair pencil as many living insects transferred to 

 them. " The specimens at once adhere, and if the spots are small 

 the insects spread out their limbs naturally, with a view to escape. 

 They may be fixed on their backs or otherwise, according to the views 

 desired. 



A very thin glass cover, or, if very high magnifying powers are 

 wanted, a small disk of clear mica, is laid over the insects, and then 

 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 filled. 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 cor- 

 nicles 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 tempera- 

 ture of a room is better than that which exceeds it. The insects die 

 immediately 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 made 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 being carried slowly outwards. 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 when the above small pressure is undesirable, small 

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



