64 REPORT — 1844. 



frequent occurrence in the interior of buildings, be examined under the 

 microscope witli a moderately higli magnifying power, tlie arrangement of the 

 spines composing the two rows whicli constitute the calamistrum will be ap- 

 parent. 



Four, six, or eight mammulas, somewhat conical or cylindrical in figure, and 

 composed of one or morejoints each, constitute the external spinning apparatus 

 of the Araneidea : they are usually closely grouped in pairs at the extremity 

 of the abdomen, and are readily distinguished from each other by their re- 

 lative positions. The pair situated nearest to the anus may be denominated 

 the superior spinners ; that furthest removed from the anus, the inferior 

 spinners ; and the mammulae placed between these extremes, the intermediate 

 spinnei's ; distinguishing them, when there are two pairs, by prefixing the terms 

 superior and inferior. Exceedingly fine, moveable papillae or spinning tubes, 

 for the most part dilated at the base, occur at the extremity of the mammulae, 

 or are disposed along the inferior surface of their terminal joint, whence issues 

 the viscous secretion of which all the silken lines produced by spiders are 

 formed. The papillae connected with the mammulte vary greatlj- in number 

 in different species of spiders, and also differ considerably in size, not only 

 in individuals of the same species, but often even on the same raammulas. 



Among our native spiders, the larger species of Epeircc have the mammulae 

 most amply provided with papillae ; it is probable, however, that the total 

 number does not greatly exceed a thousand even in adult females of Epeira 

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

 is much smaller. In Tegenaria civilis the total number of papillae does not 

 amount to four hundred ; in Textrix hjcosina and Clubiona corticalis it is 

 below three hundred ; in 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 papillae connected with the 

 several pairs of mammulae in the same species, and with similar pairs in dif- 

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

 Tetragnatha, Linyphia, Theridion and Segestria, they are generally 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 is conspicuous in Drassus ater, which has the intermediate 

 spinners abundantly furnished with papillae, those on the inferior spinners 

 being very few in number and chiefly of large dimensions, emitting the viscous 

 secretion copiously. The papilte connected with the short terminal joint of 

 each inferior spinner of this species vary in number with the age of the animal ; 

 the young, on quitting the cocoon, are provided with four only ; individuals 

 which have attained nearly a third of their growth have five or six ; those about 

 two-thirds grown, six or seven ; and adults, which have acquired their full 

 complement, eight ; two of them, situated on the inferior surface of the spinner, 

 at a greater distance from its extremity than the rest, are minute and almost 

 contiguous. It is a fact deserving of notice, that the papillae are not always 

 developed simultaneously on these spinners, six, seven, or eight being some- 

 times observed on one, when five, six, or seven only are to be seen on the 

 other ; and this remark is applicable, not to the inferior spinners alone, but 

 to the intermediate ones also, which, in mature individuals, are further modified 

 by having the extremities of the terminal joints directed downwards at right 

 angles to their bases. The same law of development holds good as regards 

 the papillae connected with the inferior spinners of Drassus cupreus and 

 Drassus seiiceus, and though their number is not uniformly the same even 



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