habited by people in the stone-using phase of life.
J. S. Patterson.
Berlin Heights, Ohio.
"A SPIDER'S ENGINEERING."
Mr. Editor: The inquiry respecting the way in which spiders bridge chasms and streams, which is made in the note with the above heading, upon page 635 of the March number of this journal, has been often and satisfactorily answered by English writers,[1] and the following is given merely as a confirmation of their more extended observations:
In March, 1866, I had taken a living male and female Nephila plumipes (sometimes called the "silk-spider of South Carolina") to the photographic establishment of Mr. Whipple, of Boston; while waiting for the taking of their pictures, and standing about six feet from the wire frame upon which was extended the female's web, I saw the little male suddenly cease climbing about the frame, and take position upon its upper margin; in a few seconds a silken thread floated near me; I allowed it to adhere to my sleeve; the spider then turned about, and made several vigorous pulls upon the line, as if to ascertain its fixity of attachment; when satisfied of this, he rapidly made his way toward me, but, in order to observe the act again, I hung my end of the line over the frame, so that he was left where he started; after a few turns he took position as before, with his abdomen elevated and directed toward the spot I had occupied; presently a fine line shot out from his spinners, and pursued an undulating course until it reached beyond the spot I had occupied, and began to rise toward the large ventilating cupola in the centre of the room; the spider would occasionally turn and try the line as before, but it did not become attached, and he did not embark upon it.
Feeling now quite sure that the current of air toward the ventilator both determined the spider's preparatory action and the progress of the line, I removed this line, and blew gently upon the spider in the opposite direction; he immediately turned about, elevated the abdomen as before, with the wind, and soon a line was carried in this direction for as long and as far as my breath could reach, and no farther. This was repeated with the same result in various directions. The extremity of the line appeared blunt and a little enlarged, which is in accordance with the view of Blackwall respecting the way in which it is started:
"The extremities of the spinners are brought into contact, and viscid matter is emitted from the papillæ; they are then separated by a lateral motion, which extends the viscid matter into filaments connecting the papillæ; on these filaments the current of air impinges, drawing them out to a length which is regulated by the will of the animal, and, on the extremities of the spinners being brought together, the filaments coalesce, and form one compound line. . . . If placed upon rods set upright in glass vessels with perpendicular sides, and containing clear water, they in vain attempt to escape from them in a still atmosphere. . . .
"The lines produced by spiders are not propelled from the spinners by any physical power possessed by those animals, but are invariably drawn from them by the mechanical action of external forces."
It is not so very strange that an American journal should reproduce the note which suggested this communication, without incorporating the desired information, since very few papers upon spiders have appeared in this country; but the conductors of Hardwicke's Science Gossip, in which it first appeared, must have been strangely oblivious of the already-quoted English accounts of the subject.
But this oversight is pardonable when compared to what occurred in Scribner's Monthly for May, 1872, in an account of spiders, evidently a compilation. The common garden spider is represented head upward in the centre of a web composed of concentric circles. Now, every one that has really examined a so-called geometrical web knows that it consists of a spiral line, and never of circles; and also knows that the Epeiridæ are as averse to reposing head upward as human beings are to assuming the
- ↑ Blackwall, "Spiders of Great Britain and Ireland" (Introduction, p. 11); Journal of Proceedings of Linnæan Society, vol. vii.; Transactions of Linnæan Society, vol. xv., p. 455.
