of the common Garden Spider. 69 J 



well as those of leaves, &c., to be considered as accidental : 

 but it must be confessed that it is difficult to explain, on this 

 supposition, the height at which the piece of gravel is some- 

 times suspended ; which, in one instance tliat 1 observed, was 

 full 6 ft. from the ground, so as to swing clear of my hat as I 

 walked under it; a height considerably more than that to 

 which it seemed to me that any probable tightening of the 

 main line, as supposed above, could have drawn up the 

 gravel ; and it therefore may deserve further investigation 

 (which is the main reason why I submit these imperfect notes 

 to the consideration of those of your readers who may have 

 an opportunity of instituting additional enquiries), whether the 

 spider, led by one of those singular variations of instinct of 

 which Huber has made known so many examples in bees, 

 does not purposely shorten the line to which the gravel is 

 attached. In one instance which came under my eyes, the 

 spider certainly seemed aware that the lower part of its net 

 was ballasted by the piece of gravel ; for, on my pulling at 

 it violently, the spider instantly darted from the centre of the 

 net down the line, and bit off the gravel, which fell to the 

 ground. We are very liable to mistake in attempting to 

 explain the motives of the actions of insects; but, if the 

 reflection had passed in the spider's mind that the gravel was 

 too heavy, and that it must, at all events, be got rid of, it 

 could not have taken a more sudden and effective step than 

 that which it adopted. 



While on the subject of the nets of Epeh^a diadema, I 

 must beg to trespass a little longer on your pages, to notice 

 a criticism of Professor Rennie, in his useful Insect Archi- 

 tecture (which work I have but lately seen for the first time), 

 on the account which we have given, in our Introduction to 

 FjUtomology^ of their general construction. 



In these geometric nets, we have said, flies are entrapped 

 on a principle quite difi^erent from that on which they are 

 caught in the webs of the common house spider (^ranea do- 

 mestica), being entangled in the thick-woven meshes of the 

 latter, but being, in fact, gummed to the concentric circles of. 

 the former, by their legs, wings, &c., adhering to the minute 

 and separate drops of a viscid gum, which may be distinctly 

 seen with a microscope to stud these circles like the beads of 

 a necklace ; while the straight rays of the net are entirely free 

 from these gummy globules, and quite unadhesive. 



On this account Professor Rennie observes as follows: — 

 " The centre of the net is said also to be composed of more 



Y Y 2 



