232 



NATURAL HISTORY. 



made up of long and delicate tubes. As lightness is a 

 great object in the structure of the Insect, the digestive 

 apparatus is made of as little bulk as possible. 



397. The feet of Insects are in conformity with their 

 modes of life. Some have claws or hooks ; some have 

 a kind of suction cushion by which they can adhere to 

 surfaces; some have fringed feet to enable them to 

 swim ; and some have their fore feet shaped for digging, 

 like the Mole's. 



398. The wings are generally made very much like 

 those of the Bat, 58. They consist of a double mem- 

 brane over an extended slender frame-work. There are 

 generally two pairs, but sometimes only one, as in the 

 case of the common Fly. Often the first pair of wings 

 are mere coverings for the other wings, and have no act- 

 ive agency in flight. In this case they are made thick 



and firm, and are called the 

 elytra (singular elytrum). In 

 Fig. 183 you see the elytra 

 at a. When the Insect is at 

 rest, the elytra are brought 

 together over the back, the 

 true wings being folded, some 

 times very curiously, under 

 them. The true wings are 

 light and thin, and they are 

 transparent, except when they 

 are covered with what ap- 

 pears to the naked eye as a 

 kind of colored dust, as is the case with the Moths and 

 Butterflies. This dust, examined with the microscope, is 

 found to be made up of little regularly-formed scales, 

 often beautifully marked with lines. When they are 

 rubbed oif, their fastenings look, under the microscope, 

 like the nail-heads on a roof when old shingles have been 

 torn oif. In some of the Butterflies the scales are ar- 

 ranged like shingles on a roof, and with their various 

 colors present a very beautiful appearance. 



Fig. 183. 



