the Mamnmlse employed by Spiders in the Process oj" Spinning. 221 



tjuadrata, whose weight is about twenty grains, and in many other species it 

 is much smaller. Each of the six mammulse, in every living Epeira whose 

 spinning apparatus I have attentively inspected, has presented one or more 

 papillae decidedly larger than the rest, which uniformly occupy the same re- 

 lative situations in individuals identical in species ; but I have not yet been 

 able to satisfy myself what especial purposes they subserve. 



Wishing to determine by experiment the strength of a line by which a female 

 Epeira diadema, weighing ten grains, had suspended itself from a twig, I at- 

 tached to its extremity a small square piece of muslin with the corners nearly 

 drawn together, so as to form a minute sack, into which I carefully introduced 

 sixty-one grains in succession, being rather more than six times the weight of 

 the spider, before it broke ; but on the addition of half a grain more it gave 

 way. 



In several species belonging to the genus Tegenaria of Walckenaer, in 

 Tegenaria domestica and Tegenaria civilis, for example, the total number of 

 papillae, does not amount to four hundred ; in Textrix agilis, Blackw., Lycosa 

 saccata, and Clubiona corticalis, it is below three hundred; in Walckenaera* 

 acuminata, Blackw., and Segestria senoculata. it scarcely exceeds one hundred ; 

 and in many of the smaller spiders it is still further reduced. 



A difference in the number and size of the papillee connected with the seve- 

 ral pairs of mammulee in the same species, and with similar pairs in different 

 species, is also very apparent. In the spiders constituting the genera Epeira, 

 Tetragnatha, Linyphia, Theridion, Segestria, and many others, they are gene- 

 rally much more numerous and minute on the inferior spinners than on the 

 superior and intermediate ones; the last are the most sparingly supplied with 

 them, and in the case of Segestria senoculata each has only three large papillae 

 at its extremity. An arrangement nearly the reverse of this takes place in 

 some of the Drassi, and may be advantageously seen in Drassus ater. This 

 species has the intermediate spinners abundantly furnished with papillae, those 

 on the inferior spinneus being very few in number and chiefly of large dimen- 

 sions, emitting the viscous secretion copiously. For the purpose of deter- 

 mining how many papillae are connected with the short terminal joint of each 



* This generic name, which, through my own inadvertency, has hitherto been printed Walckenaeria, 

 is now corrected. 



VOL. XVIII. 2 o 



