CLASSIFICATION AND DESCRIPTION OF COMMON INSECTS 367 



disease is probably transferred through the saHvary secretion of the tick. 

 Dr. Hadwen reports cases of "tick paralysis" of man and sheep in 

 British Columbia due to the bites of this species (Fig. 241). 



D. variabilis Say is a widespread form occurring on dogs, cattle 

 horses and man, but apparently is of little economic importance. 



Family Tetranychid^ (Red Spiders) 



"Red Spider" (Tetranychus bimaculatus Harvey). — (Consult Bull. 

 416, U. S. Dep. Agr., 1917; Bull. 79, Mass. Ag. Exp. St.) A common 

 pest on roses, violets, carnations in greenhouses; cucumbers in the 

 vegetable garden; and on many outdoor perennials; and a serious pest 

 in Western Colorado on fruit trees, in Central California on hops, and 

 in the Southern States on cotton. 



Adult. — Color of female variable — rusty green, amber, yellowish, 

 but more often brick red, with pigment blotches on the sides; legs 

 pale amber; palpi pale salmon; body oval, pear-shaped, 3^^o i^ch long; 

 color of male rusty salmon, body }^^q inch long. 



Eggs. — Spherical; clear becoming opaque; 50-100 eggs laid by each 

 female over a period of 7-12 days. Incubation period varies with the 

 temperature — '3-17 days. Laid singly on the under side of the leaves. 



Larval stage. — Six-legged, round and colorless; duration 2-17 days. 



First Nymphal Stage. — Eight-legged, oval, darker in color; duration 

 2-4 days. 



Second Nymphal Stage. — ^Females only have this stage; elongate; 

 duration i}^-i^ days. 



Feeding is done by means of sharp, slender, lance-like mouth-parts 

 thrust into the leaf, producing spotting. The fine webs spun on the 

 under surface of the leaf are probably protective. Reproduction is 

 both sexual and parthenogenetic. 



Control. — Spray with water; with lime-sulphur, nicotine sulphate 

 and miscible oil, linseed oil emulsion or fish oil soap, potassium sulphide, 

 kerosene emulsion; dust with finely resublimed sulphur; clean culture 

 or eradication of weeds which harbor mites during winter. 



Clover Mite (Bryobia pratensis Garman). — This is a small red mite 

 about ^00 iiich long which injures the leaves of clover, apple and 

 other orchard and forest trees by puncturing the tissues, causing them 

 to become yellowish and sickly. The winter is passed in the egg 



