398 INSECT TRANSFORMATIONS. 



ner, for it will not only drop perpendicularly by 

 spinning a longer thread (it seldom tries to escape 

 by remounting), bu.t it will swing itself away from the 

 approaching hand, in a manner which it seems not a 

 little difficult to comprehend, for it does not move a 

 limb to produce an impulse in the air, as the diving 

 spider i^Jlrgijroneta aquatica) does when it moves 

 through the water. In instances when no escape is 

 intended, when spiders, even of considerable size, 

 drop from a height, we have often seen them swing 

 out of the perpendicular without any apparent aid 

 from the wind. It is highly probable that this 

 movement is effected by some internal apparatus 

 analogous to the swim-bladder of fishes; but at 

 present we are not aware that anything beyond con- 

 jecture has been published upon the subject. We 

 may state, however, that they cannot in this manner 

 move far. 



Syrphus. 



