]90 BRITISH APHIDES. 



be drawn into a fine point. The end may be then 

 broken off; and, by warming the empty space, or still 

 better by expelling the air by a pump, a dozen or more 

 tubes may, at the same time, be entirely filled with the 

 liquid. 



The capillary tubes can then be sealed by the blow- 

 pipe flame, and the specimens may be labelled in the 

 ordinary way. 



As colours are liable to the bleaching action of light, 

 the specimens are best ranged in a dark cabinet. 

 Several liquids will be found effective, and they may be 

 varied according to circumstances. I have had 

 excellent results from very weak acetic acid, also weak 

 glycerine. If alcohol be used, it must be exceedingly 

 dilute, or it will render the insects opaque. 



But after all, for ordinary microscopic work, such 

 as taking measurements, and noticing the constituents 

 of the antennae and wings, nothing is better than care- 

 ful mounting in Canada balsam, thinned, if necessary, 

 with petroleum spirit. Just as insects are accidentally 

 preserved in amber, they may be artificially and more 

 completely secured, by embedding in any recent amber- 

 like resin. If a few simple rules be followed, there is 

 no difficulty in making these preparations ; and as to 

 their showing detail, there seems to be nothing more 

 to be desired. Although the procedure has been 

 already lightly touched on in my first volume,* a 

 recapitulation with additions may be useful. 



On a slip of ordinary-sized microscopic glass, dot 

 from the head of a pin, in any desired order, five or 

 a dozen spots of fluid Canada balsam, and by means of 

 a hair pencil transfer as many living insects 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 

 [towers arc wanted, a small disc of clear mica is laid 



* See Preface to Volume I. 



