88 THE MICROSCOPIST. 



they pull off their own bodies; and the lackey moth (Lasio- 

 campa Neustria), deposits her eggs in a spiral coil round the 

 stems of fruit trees. 



Most varieties require to be viewed as opaque objects under 

 a power of 30 to 60 diameters. 



Elytrcij or wing-cases of insects, are often singularly en- 

 graved and colored, and form the most brilliant of all opaque 

 objects. Some are covered with beautiful iridescent scales, 

 and others are furnished with branched hairs. Some of them 

 are much improved by being mounted in a thick cell with 

 Canada balsam, while others lose much of their splendor by 

 being so treated. In order to ascertain whether an elytron 

 will be improved by the balsam, one of the legs, or some part 

 supplied with a few of the iridescent scales, should be touched 

 with turpentine ; if the brilliancy be increased, it may be 

 mounted in balsam, if otherwise, dry. The elytra of some 

 beetles, after having been softened in caustic potash, may be 

 mounted between flat glasses, as ordinary objects. 



Eyes of Insects, Arachnida, &c. The structure, number, 

 and form of the eyes of insects may be ranked among the 

 most curious parts of natural history. *They are generally 

 hemispherical, on each side of the head, but sometimes they 

 are oval or kidney-shaped. When closely examined, they are 

 found to consist of a vast number of minute lenses, generally 

 hexagonal, but sometimes quadrangular or circular. In the 

 ant there are 50 of such lenses in each eye ; in the common 

 house-fly 4000 ; in the dragon-fly 12,500 ; and, according to 

 Geoffrey, in the eye of a butterfly 34,650. When one of the 

 eyes is detached from the head and cleaned, the lenses are 

 found to be as clear as crystal. If a cluster of eyes be placed 

 under the microscope, at a distance without its focus equal to 

 their focal length, the lens of each eye will exhibit a distinct 

 image of a candle, &c. ; placed before it. 



