ON COLLECTING, PREPARATION, AND MOUNTING. 385 



With regard to the preparation of the larger specimens, as, for 

 example, the female scales of Lecanium and Pulvinaria, they may be 

 boiled in caustic potash in a test-tube (not in an inner one,- as with 

 the very small species), then boiled in clean water, then transferred 

 to absolute alcohol with stain for a day, oil of cloves for another 

 day, and finally mount in xylol balsam. 



In addition to studying the more salient points of the anatomy of 

 forest insects, the student would do well to study the details of 

 minute insect structure as revealed by microscopical investigation. 

 There is obvtously no end of objects outside forest insects, thus giving 



Fig. 351. Life-history stages of " Swallow-tail " Butterfly (Papilio machaon). 

 (From photo by A. Flatters.) 



the student not only a wider outlook, but teaching him many a 

 valuable lesson from indirect subjects. Take, for example, the case 

 of figs. 349 and 350 the proboscis of the honey-bee and the tongue 

 of the house-fly. Not only do subjects like these show marvellous 

 mechanism, but they throw a strong sidelight on such delicate ana- 

 tomy as the mouth parts and feeding organs of scale-insects, green-fly, 

 &c. In the case of all insects which suck the juices from the food- 

 plant, as contrasted with those which eat the vegetable direct, it is 

 obvious that the vegetable cellular structure must be ruptured, and 

 therefore many disease spores may thus find a ready entrance into a 

 favourable host. Hence the obvious necessity of careful investigation 



1 B 



