No. 2303. RED SPIDERS OF AMERICA— McGREGOR. 669 



TETRANYCHUS SEXMACULATUS Riley. 



Plates 78 and 79, fig. 5. 

 Tetranychus sexmacuJatus ^ Riley, 1890, Insect Life, vol. 2, p. 225. 

 The original description of T. sexmaculatus by Riley is as follows: 



length of the full-grown specimens, 0.3 mm. General color, pale gi-eenish-yellow, 

 marked on the abdomen with six or less small dusky spots. General shape oval, 

 Bomewhat broadest in front of the eyes; laterally slightly constricted just opposite the 

 eyes and at about the middle of the body, at which latter constriction the body is 

 divided by a more or less distinct suture into two parts. There is often also a distinct 

 though small tail-like projection at the end of the body. Anterior projection of 

 cephalothorax rather short, somewhat conical, its apex rounded. Terminal joint of 

 legs longest. Eyes, two each side, the anterior one of each pair being blood-red, this 

 pigment extending some distance into the body giving the appearance of tv,o red 

 eyes on each side; the posterior eyes are colorless and transparent. The spots of the 

 abdomen are arranged in two subdorsal rows, of three spots to each row; they are 

 rounded and quite constant, especially in the smaller and more numerous specimens, 

 though somewhat \ ariable in the larger or full-grown mites. 



In the matiu'e specimens the anterior spots, which are arranged close to the dividing 

 suture, are often composed of a collection of 8 to 12 larger or smaller, more or less 

 circular, quite deep black spots, while in others all the spots are single, and with one 

 or the other of the median pair wanting. In the smallest specimens these spots are 

 either wanting or only the anterior or posterior pairs are present, the last pair in this 

 case being generally largest and very distinct. The distribution of the hairs of the body 

 ie as follows: Two short slender hairs medially at anterior margin, directed forward, 

 crossing each other near their tips; each side of these, also, close to margin, at about 

 equal distances from each other and the lateral margin is a pair of transparent, circular 

 pores, resembling those which usually give rise to a bristle. In front of the eyes and 

 removed slightly toward the middle is, on each side, a row of rather long and stout 

 bristles, the anterior pair being directed outward and slightly toward the head, and 

 projecting bej-^ond the lateral margin ; the median pair are directed forward and cross 

 each other near their tips. The third pair are longest, situated a little in front of the 

 eyes and directed backward. Besides these stout bristles there is another smaller 

 and slender hair not far from the lateral margin behind the eyes, and another at the 

 margin in front of the eyes. The abdomen is proAided on each side vnth a subdorsal 

 row of three very long bristles, a more slender lateral row, four long dorsal bristles sur- 

 rounding the end, and four ventral terminal bristles, of which the median pair is 

 smallest. 



The eggs are 0.11 mm. in diameter, globular, either colorless and transparent or Aery 

 pale greenish-yellow, and are loosely attached to the web. 



Riley's descriplion is too general to be of much value taxonomically. 

 Following is a condensed description from material on citrus leaves 

 from Florida: 



Body rhombic-elliptic; color lemon-yellow with blackisli spots usually grouped in 

 three blotches along each lateral region. A well-formed anterior and an abortive 

 posterior eye cornea on each side. Subfrontal bristles about one and one-half times 

 the length of the frontal bristles. Length of palpal "thumb" about equaling the 

 width of the "thumb" at tip; dorsal "finger," digituli, and three hairs very similar 

 to T. himaculatus. Tarsal appendages consist of a strongly cun^ed, 6-cleft empodial 

 claw, and four tenent hairs — all resembling T. himaculatus. Collar trachea pipe- 



1 In the original description Riley (4) dasignated the species name as "8-mac7ilatus," but later writers 

 Lave adopted the "sexmacvlatvs" form of the word. 



