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 



Spools 

 Vary. 



cvlindriciil ^lauil, tlic (Hily larji'iT i;iaiiil wliicli ilis- 

 cliargx's Iktc. On tlu' iu.siilc of tliis lioniy cone 

 is attaflied a long yellowish eord or point, upon 

 wliicli strong muscles arc iiisei'ted in order to 

 nioN'e the cone against the spinneret. 



Mr. Underhill figures the s^'igots or large spin- 

 ning tuhes wliich issue upon the posterior and 

 anterior spinnerets. ^ The former are situated upon 

 the interior margins and are connected with two 

 very large glands which are doubtless the cylin- 

 drical glands as heretofore described. These spig- 

 ots are shown at Fig. 43 together with a portion 

 of the ducts leading to their appropriate glands 

 (not represejited ) which lie below the j)yriform 

 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 sjjooIs vary greatly in number 

 in different species, and also differ considerably in 

 size not only in individuals of the same species, 

 glandular epithelium is repre- but oftcn cven On the Same spiuncrets. The larger 



sented. cy.d, ducts belonging . /• ,i -r-^ - • i t .1 



to the spigots; sp, probably of spccics ot the Jipeiroids havc the spnmerets mo.st 

 cylindrical glands, cy.g. amply provided with sjtools, and Blackwall cx- 



pres.ses the opinion that the total numljcr does not greatly exceed a tliou- 



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



twenty grains, and in many other 



species it is smaller. 



As illustrating the difference in 



various genera it may be stated that 

 Tegenaria domestica and 

 Tegenaria civilis, for ex- 

 ample, have less than four 



hundred .si)inning 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 



of the smaller spiders it is still 



further reduced. 



The difference in the number and size of the spools connected with tli(> 



several j)arts of the spinnerets in the same species, and with similar pairs 



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



Numbers 

 Vary. 



Fk;. 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 16.5. 



' Science Gossip, 1874, page 181. 



