228 FOOD OF INSECTS. 



is furnished with a multitude of tubes, so numerous and so exquisitely 

 fine, that a space often not much bigger than the pointed end of a pin is 

 furnished, according to Reaumur 1 , with a thousand of them. From each 

 of these tubes, consisting of two pieces, the last of which terminates in 

 a point infinitely fine, proceeds a thread of inconceivable tenuity, which, 

 immediately after issuing from it, unites with all the other threads into one. 

 Hence from each spinner proceeds a compound thread ; and these four 

 (or six) threads, at the distance of about one-tenth of an inch from the 

 apex of the spinners, again unite, and form the thread we are accustomed 

 to see, which the spider uses in forming its web. The threads, however, 

 are not all of the same thickness, for Leeuwenhoek observed that some of 

 the tubes were larger than others, and furnished a larger thread. Thus, a 

 spider's thread, even spun by the smallest species, and when so fine that it 

 is almost imperceptible to our senses, is not, as we suppose, a single line, 

 but a rope composed of at least four thousand strands. 2 But to feel all 

 the wonder of this fact we must follow Leeuwenhoek in one of his calcu- 

 lations on the subject. This renowned microscopic observer estimated that 

 the threads of the minutest spiders, some of which are not larger than a 

 grain of sand, are so fine that four millions of them would not equal in 

 thickness one of the hairs of his beard a tenuity utterly beyond the 

 power of the imagination to conceive. Of the probable accuracy of this 

 calculation you may any day in summer convince yourself, by taking one 

 of the large diadem spiders (Epeira Diadema), and, after pressing its 

 abdomen against a leaf or other substance, so as to attach the threads to 

 the surface the same preliminary step which the spider adopts in spinning 

 drawing it gradually to a small distance. You will plainly perceive that 

 the proper thread of the spider is formed of four smaller threads, and these 

 again of threads so fine and numerous, that there cannot be fewer than a 

 thousand issue from each spinner; and if you pursue your researches with 

 the microscope, you will find that precisely the same takes place in the 

 minutest species that spins. You will inquire what can be the end of 



1 Reaum. Mem. de lAcad. de Paris, An. 1713. 211. De Geer, vii. 187. See also 

 Hoole's Leeuwenhoek, i. 41. t. 2. f. 20 22. Leeuwenhoek examined a spinner 

 that was not so big as a common grain of sand, and the number of tubes issuing from 

 it was more than a hundred. He affirms that, besides the larger spinners, in the 

 space between them there are four smaller ones, each furnished with organs for 

 spinning threads, but smaller and fewer in number. Latreille speaks only of a 

 thousand spinners from each teat, and of six thousand threads from the whole 

 but he does not enter further into the subject. Nouv. Diet. d'Hist. Nat. ii. 278. 



2 Mr. Blackwall, however, as the result of his examinations with microscopes 

 of high powers, denies that spiders' threads are composed of so many fine lines as 

 Leeuwenhoek, Lyonnet, Treviranus, &c,, have supposed. He has not, he says, 

 found that any lines ever issue, as they describe, from the minute apertures without 

 projecting margins, situated between the papillae or spinning tubes, which last alone 

 he regards as the sole line-forming instruments, and the total number of these in the 

 larger adult species of Epeira, which are best provided with them, he does not esti- 

 mate at much above a thousand, while in the common house spider they are below 

 four hundred, and in other species not above one hundred, and in some much fewer. 

 As the statements of such careful and generally accurate observers as Reaumur, De 

 Geer, Leeuwenhoek, Lyonnet, Treviranus, and'other eminent naturalists, all in the 

 main agreeing and confirming each other, ought not to be hastily set aside and 

 without the fullest investigation, it has been thought best, without materially 

 altering the text, simply to point out in the present note Mr. BlackwalFs different 

 conclusions, and to refer the reader for the details on which they rest to his paper 

 on the Mammulaj of Spiders in the 18th vol. of the Linncean Transactions, p. 219. 



