48 



AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



Fig. 43. Anterior spinneret of 

 Epeira diademata. (After Un- 

 derbill.) ss, spinning spools ; 

 sp, spigot ; py.g, pyriform glands 

 with their ducts, py.d. The 

 glandular epithelium is repre- 



Spools 

 Vary. 



cyliiulriail gland, tlie only larger gland which dis- 

 charges here. On the inside of this horny cone 

 is attached a long yellowish cord or point, upon 

 which strong muscles are inserted in order to 

 move the cone against the spinneret. 



Mr. Underhill figures the spigots or large spin- 

 ning tubes which issue upon the posterior and 

 anterior spinnerets.^ The former are situated upon 

 the interior margins and are connected with two 

 very large glands wdiich are doubtless the cylin- 

 drical glands as heretofore described. These spig- 

 ots are showai at Fig. 43 together with a portion 

 of the ducts leading to their appropriate glands 

 (not represented) which lie below the pyriform 

 glands. Fig. 44 shows one of these anterior spig- 

 ots, a.sp, compared with two spools ss. of the same 

 spinneret. Mr. Blackwall announced the 

 fact for the first time, so far as I know, 

 that the spools vary greatly in number 

 in different species, and also diifer considerably in 

 size not only in individuals of the same species, 

 but often even on the same spiimerets. The larger 



sented. cv.d, ducts belonging . c xi m •• • i i l^ • ■ 



to the spigots; sp, probably of specics ot tlie iiij^ciroids havc the spinnerets most 

 cylindrical glands, cy.g. amply providcd witli spools, and Blackwall ex- 



presses the opinion that the total number does not greatly exceed a thou- 

 sand, even in adult females of Epeira quadrata, whose weight is about 

 twenty grains, and in many other 

 species it is smaller. 



As illustrating the diiference in 

 various genera it may be stated that 

 Tegenaria domestica and 

 Tegenaria civilis, for ex- 

 ample, have less than four 

 hundred spinning spools each. In 

 Textrix agilis and Lycosa saccata 

 the number is below three hundred. 

 In Segestria senoculata it scarcely 

 exceeds one hundred, and in many 

 (»r the smaller spiders it is still 



riii'iiii'i' i-ciiticcd. 



The difference in tlie minilx'r and size of the spools connected witli the 

 several i)arts of the spinnerets in the same si)ecies, and with similar ])aiis 

 in different species, is also very apparent. In spiders constituting the 



Numbers 

 Vary. 



Fi(i. 44. a.sp, spigot on anterior spinneret of Epeira dia- 

 demata leading to cylindrical gland; ss, spools of pyri- 

 form glands, same spinneret. (After Underhill.) X 165. 



' Srience (Jossi]), 1874, pajjc isl. 



