THE ACAEIXA OR MITES. 



35 



feed. There are about three broods a year. The winter is spent in the egg stage, 

 and also sometimes as adult. ^Vith the approaching cold of winter the mites often 

 crawl into houses seeking shelter, much to the annoyance of the occupants. Clover 

 and other infested plants 

 should not be allowed to grow 

 close to the house. Both the 

 mites and their eggs can be 

 killed by a spray of kerosene 

 emulsion; atomic sulphur is 

 used in California. Another 

 Bryobia, with longer legs, oc- 

 curs on alfalfa in the South- 

 west. 



In Tetranychus the body is 

 eubpyriform and provided 

 above with about 24 to 36 

 bristles arranged in four rows. 

 The species of this genus can 

 spin a thread, which, when 

 they are very abimdant, be- 

 comes a dense mesh or web, 

 visible at a considerable dis- 

 tance. The spinning organs 

 are said to be located in the 

 head of the mite, with open- 

 ings near the base of the man- 

 dibles, the thread combed out 

 by the palpi. The web does 

 not appear to afford the mites 

 any protection, but at times 

 seems to serve to hold the eggs 

 in place. It may be either 

 on the upper or lower surface 

 of the leaf. Ewing considers 

 that the web serves to hold the 

 mites while molting. The old 

 skins are usually found at- 

 tached to the web. In molt- 

 ing the skin splits across the 

 body over the furrow between 

 the cephalothorax and abdo- 

 men, each part being worked 

 off separately by the motions 

 of the mite. Tetranychus hi- 

 bernates in the adult condi- 

 tion. Duges has found T. tela- 

 rius Linn, under stones in win- 

 ter, and Hanstein has taken 

 them on fallen leaves and in 

 soil \mder trees. They remain 



breeding on leaves late in the autumn, even into December. Weber and Voss claimed 

 that it was the larvae that wintered, but Hanstein says he found only adult females 

 in the winter. Weldon has found T. bimaculatus Harvey in Colorado wintering in 

 the soil often 10 feet from tne tree. Most of them were found near the crown of the 



Fig. 45. — Bryobia pratensis: 



Female from above; b, lemale 

 from below; c and d, tarsal claws; e, beak from below;/, beak 

 from above; g, palpus; h,i, j,k, I, vi, scales and spines of vary- 

 ing shape. (From Riley and Marlatt.) 



