THE RED SPIDEE ON COTTON. 15 



of considerably greater length and prominence, the frontal pair not 

 over half as long as the subfrontal pair, which, like themedian pair next 

 behind, are in length equal to two-thirds the greatest width of the body. 

 Relatively the legs are longer in the male than in the female. Tip 

 of upper side of thu'd joint of palpi with a short, stout, curved spine. 

 The penis (Ewing, 1913) is short, stout, and has a hook at its end 

 which turns upward and ends in a flattened barb. A measured 

 series of males yielded the following dimensions: Length (anterior 

 margin of cephalothorax to tip of abdomen), 0.256 mm.; width, 0.142 

 mm.; foreleg, 0.256 mm. 



Color variations. — The color variations of the male are very slight 

 compared with those of the female. Nearly all individuals conform 

 to one type, which is of an amber-yellow color. 



GENERAL FEATURES. 



Structural variations. — The microscopic characters of the palpus of 

 the red spider (PI. Ill, figs. 1 to 7) are rather variable. The relative 

 dimensions of the terminal 'finger" show considerable diversity. 

 The number of bristles between the terminal "finger" and the sub- 

 basal "finger" varies at least from 1 to 3; also, the size and out- 

 line of the sub-basal "finger" is subject to some variation. (PI. Ill, 

 figs. 13, 14.) Similarh'-, the character of the tarsal appendages (PI. 

 Ill, figs. 8 to 12) exhibits some modifications. 



Proportion of sexes. — Worsham (1910) states that in Georgia less 

 than one-fourth of the fertilized eggs produced males. In a large 

 number of rearing tests conducted at Batesburg the total male and. 

 female progeny from fertilized eggs was found to be 39.7 per cent 

 and 60.3 per cent, respectively. The ratio of four males to six females 

 represents fairh^ well the usual proportion of the sexes. When de- 

 velopment is normal, the ratio of females to males (based on the 

 foregoing computation of sex ratio) will remain about six to four. 

 At the time of the active migratory movements of females, with their 

 resulting isolation without male individuals, reproduction takes place 

 parthcnogenetically for awhile. Since unfertilized eggs invariably 

 bring forth male individuals, the progeny of these isolated unfertilized 

 migrants will be males, and following such migrations a superabund- 

 ance of males is frequently observed; also, the ability of males to 

 evade capture by predatory enemies or to withstand the action of 

 wind and rain may account partly for the increased number of males 

 which occurs at times. In the fall there is a tendency for th(^ males 

 to predominate which insures the fertilization of the females during 

 the winter. 



Copulation. — Several writers have dcs(;ribed the act of copulation 

 of the red spider. Perkins (1897) states that the sexes pair at once 

 after the last molt atid that oru; female may receive several males if 



