66 AMERICAN SPIDERS AND THEIR SPINNINQWORK. 



Rev. 0. p. Cambridge^ accounts for the great lessening in size of some 



male spiders, as Nepliila, in comparison with that of the female, 

 Dispro- by a kind of sexual selection. It is obvious, he reasons, that 

 portion- ^j^g smaller the male the better liis chance of escape, and thus 

 in Sexes selection would operate until males became so small as only just 



to be able to fulfill the office of impregnating the female. 

 It is perhaps difficult to reason upon this subject without a much larger 

 array of facts than we at present possess, but there arc some points which 

 may be remarked upon with advantage. And it is to be noted that, in the 

 case of Orbweavers, the extremely diminutive size of the male obtains in 

 those species whose females have acquired the largest development. For 

 example, our indigenous Argiopes are among the largest of the tribe, and 

 their partners are very small, not exceeding one-fourth the female's size. 

 The same is true of Nephila wilderi of our Southern seaboard, and in the 



case of the large Nephilas of tropical countries, as, for example, 

 Disad- ti-ie Nephila nigra of Vinson (see Fig. 6, page 27), the differ- 

 vantages ^^^^^ j^ ^^^^ ^^^^.^ remarkable. Now, it is certainly true that, 

 Size ^^^^'^ ^^^ male of a size corresponding with the female, his weight 



upon the orbicular snare of the genus would appear at first sight 

 to be a disadvantage in several respects. First, it might break down and 

 injure the snare, and thus place a serious obstruction in the way of nat- 

 ural union. 



Again, the advent of such a bulky creature upon the snare would at 

 once advise the female of invasion by a most formidable stranger, and 

 the natural instincts of the occupant of the web would be to regard that 

 stranger as hostile, so that her natural ferocity would be awakened, and. 

 the chances for combat and loss of life, or the prevention of sexual union, 

 would be a pretty certain result. From this view of the subject, Mr. Cam- 

 bridge's suggestion, that the diminution of size would be a great advantage 

 to the male of these largo species in accomplishing his amatory purpose 

 and protecting his life, has somewhat to support it. 



But, on the other hand, it may be said that the immense snares of 

 Nephila and Argiope are no more fragile in proportion than those of 



smaller sized Orbweavers, in whose case the sexual disparity ' does 

 t,^^ not exist. Again, it might well be reasoned that natural selection 



might have operated quite as favorably by maintaining the pro- 

 portionate size of the male or even preserving the largest examples of that 

 sex, inasmuch as increased strength would make him more formidable and 

 thus better fitted to accomplish his purpose. In other words, there is no 

 reason why Nature should not have preserved or bestowed the advantage 

 of superior strength, as well as the advantage of insignificance in size and 

 therewith, perhaps, corresponding caution and ingenuity in approach. As 



' Zoologist, 1868, page 210, and Proceedings Zool. Soc. Lond., 1871, page 621. 



