680 THE POPULAR SCIENCE MONTHLY. 



cohesion. It is a remarkable fact that the spinnerets are under the 

 prompt control of the spider's will, so that, in dropping from a height 

 by the rapidly-forming hne, the descent can be instantaneously 

 stopped at any point. It is equally curious that, in ascending the line, 

 a spider winds up the superfluous cord into a ball, and has a special 

 claw or comb inserted between the others for the purpose. 



Some kinds of spiders take to ballooning or migrating from place 

 to place through the air. For this purpose they spin those long, loose 

 and amazingly attenuous threads called gossamer, which exert a buoy- 

 ant influence by which the animal is enabled to commit itself to atmos- 

 pheric currents and move from place to place, and by which it gains 

 the partial advantage of wings. 



In the construction of webs for the snaring of its prey, the re- 

 sources of the spider are endless. Dr. Samuelson, from whose admi- 

 rable monograph our illustrations are taken, says : " "With wonderful 

 rapidity and instinct, the spider employs these threads to weave its 

 web, or wanders from place to place, often constructing a perfect net, 

 to entrap its prey, upon accurate geometrical principles, in less than 

 an hour ; and, what is most remarkable of all, performing this task in 

 what to us would be total darkness. There are many other curious 

 and mysterious circumstances connected with these webs. The gar- 

 den-spider, for instance, covers all the concentric filaments of its net, 

 at regular intervals, with glutinous or adhesive globules, presenting 

 under the microscope the appearance of pearls strung upon a thread, 

 and destined to facilitate the capture of its prey." 



The work of the geometrical spiders may at almost any time in 

 the proper season be observed in the garden. As the flight of insects 

 is mainly in an horizontal direction, the net is usually fixed in a per- 

 pendicular or somewhat oblique position to intercept them. The first 

 thing is to enclose a space with strong lines as a kind of frame, within 

 which the web is to be formed. It is immaterial what is the shape of 

 this enclosed area, as the spider is aware that she can as well inscribe 

 a circle in a triangle as in a square. But these outside lines must be 

 strong, and so they are formed of several threads glued together and 

 attached to various objects of support. Mr. Spence thus describes 

 the subsequent construction : " Having completed the foundations of 

 her snare, she proceeds to fill up the outline. Attaching a thread to 

 one of the main lines, she walks along it, guiding it with one of her 

 hind-feet that it may not touch in any part, and be prematurely glued, 

 and crosses over to the opposite side, where, by applying her spinners, 

 she firmly fixes it. To the middle of this diagonal thread, which is to 

 form the centre of her net, she fixes a second, which, in like manner, 

 she conveys and fastens to another part of the lines encircling the 

 area. Her work now proceeds rapidly. During the preliirir/ary oper- 

 ations she sometimes rests, as though her plan required meditation. 

 But no sooner are the marginal lines of her net firmly stretched, and 



