THE SENSES AND THEIR ORGANS. 287 



Rev. Mr. Pickard-Cambridge ' records that he has more than once seen 

 an English Urbweaver, Meta segmentata, drop from her web upon an insect 

 which it had espied on the ground a little way below it, and ascend again 

 with its prize by means of the line drawn from its spinnerets in the de- 

 scent. This is certainly a remarkable degree of keensightedness for an 

 Orbweaver, one, by the way, that habitually affects a shadowed habitation. 



Many species of Orbweavers are found upon their snares during day- 

 time in normal posture for capturing prey. Tliey seem to have little 

 cessation of activitj^ in the hours of light, nor does there appear 

 ^?^ to be special increase of activity during evening. Other species, 



as the Furrow spider, quite habitually exclude themselves from 

 the orb during the day and hide in the vicinity until the approach of 

 evening, when they come forth and take position at the hub of the orb. 

 With most species this is the time when such work will be done. As the 

 light begins to diminish over the landscape an increased activitjf^ may be 

 observed throughout a large part of si)ider world, and everywhere indi- 

 viduals may be seen flying tentative filaments, restlessly pioneering the 

 neighboring shrubbery, ruiming foundation lines, weaving webs, swathing, 

 trussing, eating insects. Sometliing of the same sort may be seen in the 

 early morning, when snares broken by the night's work are renewed or 

 re])laced. 



III. 



I am not prepared, as yet, to say whether a comparison of the species 

 which show morning activity with those which display activity at night 

 would justify a separation into nocturnal and diurnal spiders. Certainly 

 the line would not be a rigid one ; but there is some ground to .suppose 

 that there are occasional tendencies to this side or that, more or less de- 

 cided. There is probably a difference in this respect among the several 

 eyes of any one spider ; some are undoubtedly organized to re- 

 Color of ggjyg more light than others, while some receive the image pict- 

 ^^^' ured in greater detail. (Fig. 282.) We may therefore attribute 

 different powers of vision to the different eyes. The eyes of spiders vary 

 both in shape and color in the same individual. Some are pearly white; 

 others yellowish, amber, dark gray, or black. Some Saltigrades have eyes 

 that shine like precious stones, reflecting various brilliant hues, as the 

 emerald, the amethyst, the opal — which may be due, in part at least, to 

 reflection from the brilliantly colored mandibles. These hues, according 

 to M. Simon, indicate different powers of vision and cjualities of service. 

 Quoting favorably a remark of Dr. Vinson, he would divide a spider's 

 eyes into " diurnal " and " nocturnal." The diurnal eyes are brilliant, 



' Sjiiilers of Doi-set, Vnl. II., page 241. 



