FOOD OF INSECTS. 263 



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

 furnished, according to Reaumur^, 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.^ But to feel 

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

 calculations 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 spin- 

 ning — 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 

 machinery so complex ? One probable reason is, that it was necessary 

 for drying the gum sufficiently to form a tenacious line, that an extensive 

 surface should be exposed to the air, which is admirably effected by divid- 



» Reaum. Mem. del' Acad, de Paris, An. 1713. 211.— DeGeer, 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 hun- 

 dred. 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 thou- 

 sand threads from the whole — but he does not enter further into the subject. Nouv. Diet. 

 d'Hist. Nat. ii. 278. 



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

 powers, denies that spiders' threads are composed of so many tine lines as Leeuwenhoek, 

 Lyonnet, Treviranus, (Sec, 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 estimate at much above a thousand, while in the com- 

 mon house spider they are below four hundred, and in other species not above one hun- 

 dred, 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. Blackwall's different conclu- 

 sions, and to refer the reader for the details on which they rest to his paper on the Mam- 

 mulae of Spiders in the 18th vol. of the Linnean Transactions, p. 219. 



