96 THE ANIMAL KINGDOM. 



transverse horny ridge, furnished with numerous short 

 transverse ridges or teeth, and forming a kind of bow or 

 file. The insect rubs the Elytra across one another, and 

 the grating of the files/ together with the action of the 

 drum as a sounding board; causes the loud chirp. Some 

 naturalists think that the legs work against this file and 

 produce the sound, particularly in the Grasshopper, whose 

 thighs are armed with rough ridges and short spines, and 

 act as the bow against the files and drum of the Elytra. 



The male Cricket only chirps. The female, silently at 

 home, occupies herself in laying about 300 eggs and in 

 rearing her brood. The tongue of a cricket is a beautiful 

 object. 



SCALES OP INSECTS. 



The feathers of a Moth, a Butterfly, a Gnat, the scales 

 of a Beetle, of a Weevil, of the Podura, are all both favorite 

 and useful objects for the microscope. It is well known to 

 every one that the dust which remains on our fingers after 

 touching a butterfly's wing is a mass of beautiful feathers, 

 or scales, varying in shape and colour with the species ; and 

 that some are so delicately ornamented with a tracery that 

 no unassisted eye can see, that they form test objects for 

 the defining power of the microscope. 



Besides that use, we learn much from viewing a part of 

 a butterfly's wing as an opaque, and observing how the 

 scales are arranged on the membrane of the wing exactly 

 like the tiles on the roof of a house ; this is called being 

 " imbricated ;" each scale furnished with a point at one 

 end which fits into a cup-like socket, attached to the skin 

 of the body or the membrane of the wing. When the scales 

 are rubbed off and transparent, we can better observe their 

 structure, and we have some excellent examples in the slides 

 numbered here. 



SCALES OF MORPHO MENELAUS. 



Each scale or feather consists of three distinct laminae, 

 two external and coloured, the inner one a highly polished 



