THE TRIANGLE SPIDER : THE ORB SECTOR. 



189 



Slack 

 Line. 



backward, and also clasp the trapline in the approximated claws. But be- 

 tween the third and fourth pairs of legs the trapline presents a peculiar 

 form. Instead of being drawn taut or held loosely, it has the 

 appearance of a coil, and this in fact it is. About three-fourths 

 of an inch of the trapline, or a portion equal to four times the 

 entire length of the spider, is rolled up above the spinnerets and 

 the hinder part of the abdomen, between the third and fourth pairs of legs. 

 (Fig. 179, cL) Behind the spider the trapline is in the same taut condi- 

 tion that it presents in front of the spider. 



The net is now in perfect condition for operation. The whole front 



part of it, which includes the snare proper, is drawn taut in every cord 



and fibre. (See Fig. 180.) The trapline behind the spider is in 



ui&ing' the same tense condition. The only portion that is relaxed is 

 the Snare. 



the bit of coil between the last two pairs of legs, and occasion- 

 ally (perhaps) the short 

 stretch between the front 

 legs and the third pair. We 

 will now suppose that an 

 insect strikes the snare, al- 

 though the same effect can 

 be produced by touching the 

 spider herself or by tickling 

 the fibres of her web in a 

 manner to imitate the move- 

 ment of a fly. She is not, 

 however, easily deceived by 

 the latter trick ; at least, I 

 have rarely been success- 

 ful enough to compel her to spring her net by mimicking the move- 

 ments of an insect, and when I desired to make the observation, was 

 compelled to touch her gently with a penciL As soon as the spider per- 

 ceives that her prey is trapped, she unclasps simultaneously all the fore 

 feet holding upon the trapline, and those of the third pair of legs which 

 keep relaxed the coil of slack line. Instantly the entire snare shoots 

 forward (Fig. 181), and by a principle of inertia which needs no expla- 

 nation, the spiral lines are thrown forward around the insect (Fig. 182), 

 whose entanglement is thus secured. With a rapidity so great that the 

 eye is not able to follow the details of the movement, the snare is tight- 

 ened ; the spider momentarily assumes the previous position of expectancy, 

 and again springs her net. This may be repeated several times, Wilder 

 having observed six successive springings of the net. 



In this movement the spider appears to shoot forward with her snare, 

 but in point of fact she has remained stationary, or at least has advanced 

 but a trifle. But now, crawling to the apex of her snare, she seems to 



FIG. 181. A relaxed snare of Hyptiotes, after the snap. 



