OF MICROSCOPIC OBJECTS. 109 



to protrude, when it must be secured by the same means a 

 the foot, and may be subjected to the soaking in turpentine, 

 and mounted as usual. The honey-bee is, however, very 

 different in formation, and is well worth another slide j 

 indeed, even in insects of the same class, the differences are 

 many and interesting. There is another good friend to 

 the Microscopic Cabinet, the large water-beetle, " Dyticuz 

 marginalia" ; and he is by no means uncommon, as he may 

 be met with in many old ponds. If his wings are taken, 

 dried, and mounted in balsam, beautiful circles with crosses 

 make their appearance when examined by the aid of 

 polarized light. But what are commonly termed his 

 suckers are perhaps, his most popular gifts. On his an- 

 terior legs will be found small discs attached to central 

 members (making the whole an exact resemblance of a boy's 

 sucker), which may be readily cut off, placed on the slide, 

 and mounted in balsam. The Dyticus also gives splendid 

 examples of spiracles ; but this will be mentioned where 

 dissection is treated of. 



Another worthy object of study is the respiration of 

 insects, which is effected by tracheae or hollow tubes, which 

 generally run through the body in one or more large trunks, 

 branching out on every side. These terminate at the sur- 

 face in openings, which are termed spiracles, or breathing 

 organs. The trachece often present the appearance of tubes, 

 constructed of a spiral thread, somewhat resembling the 

 spiral fibres of some plants. These are very beautiful 

 objects, and are generally mounted in balsam, for which 

 reason they are mentioned here; but as they evidently 

 belong to the dissecting portion, they will be fully treated of 

 in another place. 



Amongst the parasitic insects a great variety of micro- 

 scopic subjects will be found. As these are usually small, 

 they may be killed by immersion in spirits of turpentine ; 

 and, if at all opaque, may be allowed to remain in the 

 liquid until transparent enough, and then mounted in 

 Canada balsam. 



