THE ARACHNIDS AND THE MYRIAPODS 121 



display not only of their grace and agility but also of their 

 beauty before the females, and that the females after atten- 

 tively watching the dances and tournaments which have been 

 executed for their gratification, select for their mates the 

 males that they found most pleasing, points strongly to the 

 conclusion that the great differences in color and in ornament 

 between these spiders are the result of sexual selection." 



Harvestmen. The long-legged harvestmen, or daddy-long- 

 legs (Liolu'num, Fig. 63), are allied to the spiders. They 

 can be recognized by the eight extremely long legs, which are 

 thus developed as organs of touch, as well as for walking. 

 They are harmless creatures, found in damp and shady places ; 

 they feed on small insects, especially aphids. 



Mites and Ticks. The mites and ticks are related to the 

 harvestmen and to spiders. They show less segmentation of 

 the body than the preceding groups. They are small, oval, 

 eight-legged forms. The mouth-parts are more or less united 

 to form a beak. Some are parasitic on other animals (Ixo'des, 

 Fig. 64) ; others, 

 like the common 

 red mite which in- 

 fests house-plants, t&^^&^S&.M- A 

 suck the fluids of 

 vegetation. One of 

 them produces the 

 disease known as 

 mange, among 



dogs, horses, and FIG. 04. Cattle-Tick. Enlarged. (After Howard, 

 COWS. Year-book, Department of Agriculture, 1891) 



Scorpions. The 

 scorpions have the 

 body plainly segmented. In the common scorpion (Bu'thus, 

 Fig. 65), found under sticks in our southern states, the 

 maxillae are greatly elongated, making a formidable-looking 



A, parasite without food ; B, parasite rilled with blood 

 from host 



