INSECTS AND THEIR NEAR RELATIVES 



19 



The majority of mites are very small but a few, especially the ticks, 

 are of considerable size. The mode of life of the different members of 

 this order varies greatly; some are parasitic upon animals; others infest 

 living plants; and many feed upon dead animal or vegetable matter, 

 thus acting as scavengers. 



Among the mites that are parasitic upon animals are the various ticks, 



Fig. 36. — The southern 

 cattle-tick, Bnophilus annulaius. 



Fig. 37. — An Itch-mite: 

 below; b, from above. 



a, from 



which are very common in the warmer parts of our country. The com- 

 mon cattle-tick (Fig. 36) of the southern states is a very injurious parasite 

 of cattle because it not only sucks the blood of its host but it carries from 

 one animal to another the organism which causes a serious fever among 

 the cattle known commonly as Texas-fever but more properly splenic 

 fever. 



The itch-mite is a well-known parasite, infesting man and causing 

 the disease known as itch. The sensation characteristic of this disease 

 is due to the burrowing of the mites in the skin; and the efficiency of 

 sulphur ointment in checking this disease is due to the fact that by the 

 use of it the mites are killed. Figure 37 represents an itch-mite greatly 

 enlarged. 



Parasitic mites are frequently found attached to insects; a common 

 species occurs beneath the wings of locusts. 



The best known of the mites that infest plants is the one commonly 

 called the red spider. This lives upon house-plants; and in the warmer 

 parts of the country, it infests fruit-trees, cotton, and other plants in 

 the open air. On house-plants and in the greenhouse it can be subdued 

 by a liberal use of water. 



Some of the mites that infest 

 plants produce galls. These galls are ^x J*s?£$firi 



of various forms, but differ from those 

 produced by gall-flies (Family Cynip- 

 idce of the Order Hymenoptera) in 

 having open mouths, from which the 

 young mites escape. 



A common disease of the pear, 

 caused by the pear-leaf blister-mite, 

 is produced by a four-legged mite Phyllocoptes pyrl, (Fig. 38). The blisters 

 characteristic of the disease are swellings of the leaf, within which there 



Fig. 38. — Phyllocoptes pyri, greatly enlarged. 



