116 FIRST BOOK OF ZOOLOGY. 



It may be observed, too, that the net does not stand vertical, 

 but leans a little, and the spider having completed the net 

 takes a position in the actual centre of the net, head down- 

 ward and on the inclining side of the net. With its legs 

 outstretched, and resting on the radiating lines, it can feel the 

 slightest jar or agitation made by a struggling insect. The 

 spider being above the true centre of the net and on the in- 

 clining side, if the fly has become entangled below the centre, 

 it can instantly drop to the desired point suspended by the 

 ever-ready thread which it makes, and, swinging to the net, 

 it almost instantly catches the fly. 



The pupils would do well to watch the spiders while they 

 are constructing their nets, and to observe and describe, or 

 sketch in outline, the different kinds of nets they find and 

 the kinds of spiders which construct them. 



107. Besides the nets made by spiders to ensnare insects, 

 some species have the power of running out a long thread 

 which answers the purpose of a balloon in raising them from 

 the ground and carrying them floating a long distance in the 

 air. In constructing this buoyant means of transportation, 

 the spicier does it at peculiar times of the day, and in peculiar 

 positions. Selecting some place where the heated air is rising 

 from the ground or from the side of a fence, it turns up 

 its abdomen and allows the rising current of air to carry 

 upward the thread which is being made, and, when this thread 

 is of sufficient length for its buoyancy to overcome the weight 

 of the spider, it floats away with the spider hanging below. 



The following represents the young spider in the atti- 



