ACARINA OR MITES. 107 



all minute and transversely wrinkled. They have only four 

 legs, the two hind pairs being reduced to simple bristles. The 

 mites live in the buds and leaves of plants, and produce 

 galls. 



Family Trombididae. — The Eed-spider of the hop, Tetrany- 

 ehus telarius, may be taken to exemplify this family. They 

 are extremely variable in colour, some being green, others 

 rusty-red, others almost white ; often dark specks are seen upon 

 them, and in not a few instances brown individuals may be met 

 with. This varied coloration is due to both age and food. 

 These mites are so minute that they can scarcely be seen on the 



Fig. 42. — Red Spider (TetranycUus telarius). 

 A, Eggs on leaf ; u, larva ; u, foot of mite ; jj, adult. 



leaves without a lens. This and some others of the genus spin 

 webs of fine silk on the under-sides of the leaves. The legs, 

 which are provided with bristles, take a prominent part in the 

 weaving of this web, guiding the microscopic silken thread as it 

 issues from the conical papilla near the anus of the mite. 

 In and under this webbing the mites live and breed. The 

 females lay their rather large globidar eggs in this web. Some- 

 times the ova are colourless, at others they have a golden hue. 

 Incubation takes place in from six to eight days, the young 

 or larval mite being colourless, and has only six legs. After 

 repeated ecdj^ses, the normal number of legs is attained. All 



