THE EED SPIDER ON COTTON. 13 



cephalothorax to tip of abdomen; relative lengths of segments of 

 leg I, coxa 25, trochanter 15, femur 53, patella 23, tibia 30, tarsus 

 49; femur almost 4 times as long as thick; tip of tarsus (the onych- 

 ium) bearing a claw which is strongly arcuate and 4-cleft to its 

 middle. Ai'ising also from the onychium, laterad of base of claw on 

 either side is an enlarged process which immediately splits into 2 

 nearly straight hairs, each of which bears a capitate tip. These 4 

 capitate hairs spread spokelike in the same plane and their relative 

 lengths are similar to those of the fingers of the human hand viewed 

 from the top. The location of bristles near the onychium is not 

 constant, varying with the locality, etc., 1, 2, or 3 hairs occurring at 

 the point of abrupt enlargement near the tarsal end which reach 

 almost to the tips of the capitate hairs, and 2, 3, or 4 hairs occurring, 

 at a distance from the onychium about twice as great as that of the 

 distal hairs. (PI. Ill, figs. 13, 14.) A series of measured females 

 gave the following dimensions : Length (front of cephalothorax to tip 

 of abdomen), 0.424 mm.; width (across posterior margin of cephalo- 

 thorax), 0.278 mm.; length of foreleg, 0.325 mm. 



Longevity. — The duration of life of the adult female may be divided 

 into two periods — a short period inmiediately following the deuto- 

 nymphal molt during which no eggs are laid, and a rather extended 

 egg-laying period, which, as determined by experiments at Batesburg, 

 is 18.8 days. Perkins states that in warm, dry weather the female 

 begins to oviposit in about 48 hours after the last molt, and that in 

 cooler weather egg laying may not begin for several days. Von 

 Hanstein (1901) found the preoviposition period of Tetranychus althaea. 

 to be eight days or more. Ewing (1914) records the average duration 

 of the period previous to egg laying to be three and four-fifths days. 

 During this inactive period the female mates, feeds to some extent, 

 and exhibits a desire to migrate. 



The adult life, from the last molt to death, as computed from 23 

 females, is 12.43 days for the summer season in South Carolina. The 

 longest individual record of longevity at Batesburg is 39 days, cover- 

 ing a period from September 1 to October 9, most of which was dur- 

 ing v/arm weather. The next longest record was 23 days, covering a 

 period from September 1 to September 24, also during warm weather. 

 Perkins states that in Vermont the females under favorable conditions 

 may hvc at least three weeks and probably longer. Ewing found the 

 average longevity of the female during the early fall in Oregon to be 

 21 J days. Morgan (1897) claimed that females live only from five to 

 seven days after reaching maturity. The virile late-fall female often 

 lives five months. Very little is known conceniing the longevity of 

 the male. 



C'olf/r variations. — ^That red spiders vary in color has been observed 

 for a long time. It was observed in the case of the European spe- 

 cies, and seems to have \uh'1\ iiistrumcMital largely in IIk^ foi'ination 



