OF MICROSCOPIC OBJECTS. 109 
to protrude, when it must be secured by the same means as 
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; 
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, “ Dyticus 
marginalis” ; 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 tracheze 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 trachec 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 tke 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. 
