186 Mr. Blackball on the Construction of the 



quantity of water completely to immerse their bases, the Spiders, thus 

 insulated, use every means in their power to effect an escape ; all their 

 efforts, however, uniformly prove unavailing in a still atmosphere ; never- 

 theless, when exposed to a current of air, or when gently blown upon 

 with the breath, they immediately turn the abdomen in the direction of 

 the breeze, and emit from the spinning apparatus some of their liquid 

 gum, which being carried out in a line by the current, becomes connected 

 with some object in the vicinity. This the Spider ascertains by pulling 

 at it with her feet, and drawing it in till it is sufficiently tense, she gums 

 it fast to the twig, and passing along it speedily regains her liberty. 

 Now, that the same means are frequently resorted to by Spiders in their 

 natural haunts, for the purposes of changing their situation and fixing the 

 foundations of their snares, I have repeatedly observed. I am aware that 

 in the Introduction to Entomology an objection has been urged against 

 the explanation of the difficulty here insisted upon. " If," say the 

 learned authors, " the position of the main line be thus determined by 

 " the accidental influence of the wind, we might expect to see these nets 

 " arranged with great irregularity, and crossing each other in every direc- 

 " tion ; yet it is the fact, that however closely crowded they may be, 

 " they constantly appear to be placed not by accident but design, com- 

 *' monly running parallel with each other at right angles with the points 

 " of support, and never interfering." In favourable weather, it is well 

 known, that the geometric Spiders usually begin to construct their nets 

 soon after the close of day, and as similar processes must be influenced 

 in a like manner by the simultaneous operation of the same cause, the 

 lines of individuals carried out by a current of air till they become at- 

 tached to some distant object, will be all parallel or nearly so. This 

 regularity, therefore, instead of militating against the opinion maintained 

 above, appears to me to furnish a povt'erful argument in support of it. 



Sometimes the geometric Spiders suspend their nets in places not 

 entirely surrounded by objects to which, in the first instance, they can 

 proceed and attach their boundary lines. In such cases their operations 

 are deserving of attention. After spinning a few radii, which, are fixed 

 to several distant points most accessible to her, the Spider fastens a thread 

 to one of them, gluing it to that extremity which is farthest from the 

 centre of her net. Along this radius she walks, drawing out the thread 



