Kew : Snares or Snap-nets of Triangle Spiders. 



Fig. 2 (after McCook : reduced) represents a snare of 

 this spider, spun on a dry bush in a New England stone- 

 fence. According- to McCook, the structure is usually placed 

 low down, rarely more than three or four feet from the ground. 

 It is generally more or less vertical ; but perhaps never abso- 

 lutely so, being usually somewhat inclined ; often, as stated by 

 Wilder, at an angle exceeding 45° ; and McCook mentions 

 having occasionally found it more or less horizontal. According 

 to Wilder's papers these snares are the work of females only, 

 the males being believed to get a precarious living by hanging 

 on to the snare of a female ; Wilder admits, however, that 

 young males may possibly spin snares ; and it has since been 

 ascertained by McCook that the males make snares exactly like 

 those of the females ; though here, as in Epeirids, males may 

 sometimes be observed, during the breeding season, about the 

 outskirts of the snares of females. As described by Wilder : — 



The net is triangular in form and consists of four radii, never more or 

 fewer, crossed by several (6-10) independent viscid lines ; the centre of 

 radiation is prolonged into a single nearly horizontal strong and short line 

 which is attached to a branch or twig- ; the outer ends of the radii are 

 attached to a second strong- line more or less nearly vertical and nearly at 

 right angles with the first. 

 Or, as stated by McCook : — 



The appearance which the snare presents to the observer is that of 

 a circular sector, attached at the open or outer end to surrounding objects, 

 and at the apex to a straight line of varying length, similarly anchored. 

 The number of radii is always four, never more nor less, and in this 

 number, of course, are included the two outside rays. The two central 

 radii are crossed by lines which may be regarded as the equivalent of the 

 spiral lines which intersect the radii in ordinary orbwebs. 

 The fact that the radii are constantly four in number is of 

 interest, for uniformity in matters of this kind is exceedingly 

 rare among spiders. In a hundred or more snares examined by 

 Wilder there was no variation in this respect, and very numerous 

 observations by McCook confirm that the number is invariably 

 four. The radii do not, as a rule, diverge from a common 

 point, so that there is ordinarily no true centre of radiation. 

 This want of a common starting-point is well show n in Figs< 2 

 and 3: both from drawings of actual webs; but it is not 

 indicated in Thorell's description of the European snare, or in 

 EmertOn's description and figure of the snare of the present 

 species ; Wilder's drawings (Figs. 4-6), moreover, show the 

 radii running from points nearer together, apparently, than is 

 usual in nature. Sordelli's drawing (Fig, 1) makes it clear that 

 a common centre is wanting in the European snare, and in his 



1900 July j. 



