igo 



HOUSE, GARDEN, AND FIELD 



press than as an organ of mastication. The crayfish furnishes 

 a third example of an animal in which the mixing and masti- 

 cation^of the food is^performed by internal teeth far from 



the mouth. All three agree in 

 this, that their internal teeth 

 are placed in the mouth-sec- 

 tion of the alimentary canal, 

 which is formed by an inward 

 growth of the epiderm, and in 

 Arthropods is lined by the 

 same kind of chitinous skeleton 

 as covers the outside of the 

 body. 



In the house-cricket both 

 sexes are winged. The fore 

 wings (wing-covers) almost 

 conceal the folded hind wings, 

 which project behind as two 

 slender tails. Each wing- 

 cover is adapted to the shape 

 of the body, being broad and 

 flat where it covers the back 

 and bent down at the sides as 

 if hinged. When at rest, the 

 right wing- cover usually over- 

 laps the left. All this is the 

 same in both sexes, but a 



closer examination shows that the pattern formed 

 by the veins differs. In the female the wing-cover is 

 covered by a radiating system of veins, not unlike that 

 found in the male cockroach, but in the male cricket 

 the veins are curiously distorted. There is a large space 

 nearly clear of veins, which appears to act like a sounding- 

 board or resonator. The microscope shows, near the 

 junction of the basal third with the rest of the wing- 

 cover, a strong bent vein starting from the inner border, 

 and this is seen to be set with innumerable cross-ridges, 



FIG. 41. Wing-cover of male 

 house-cricket. The lateral portion, 

 which is bent down at a right angle, 

 is separated. The file is shown as 

 a bent line with cross markings, 

 and just below it is the roughened 

 triangular space, against which the 

 file is rubbed ; the resonator comes 

 beneath this again. Magnified. 



