PHYSIOLOGY OF INSECTS. 121 



CHAPTER IV. 



OF THE WINGS AND LEGS OF INSECTS. 



434. THE wings and legs of insects are situated 

 in equal numbers on each side of a right line drawn 

 down the back ; they constitute five pairs, four 

 wings and six legs. 



435. The fore wings (proalce) arise from the 

 sides of the mesothorax ; they vary in compo- 

 sition, covering, and form, and their variations 

 afford excellent distinguishing characters. 



436. Scaly fore wings (proalcz squamosce) are 

 membranaceous, and covered with a coat of 

 minute scales placed in rows ; the edges of the 

 scales in one row, covering the insertions of those 

 in the next, like the scales of a fish, or the tiles of 

 a house : these wings are used principally in 

 flight. The wings have this character in the 

 butterfly. 



437. Membranaceous fore wings (proalce mem- 

 branacece) are composed of a delicate transparent 



