246 THE ENTOMOLOGIST. 



very delicate waving hairs which ai'e found on the upper 

 surfaces of their legs : duiing life they move at their pecu- 

 liarly cup-shaped bases with the least motion of the atmo- 

 sphere, but are immovable after death. It is well known 

 that sound is due to vibrations which are generally conveyed 

 by undulations of the air: now I am perfectly satisfied that 

 if these undulations are of a certain character the hairs I am 

 alluding to upon the spider's leg will move, and I wish you 

 particularly to notice that they are of different lengths, so 

 that some might move whilst others would not, and also that 

 the longest is at the extremity of the leg, and therefore can 

 receive an undulation which might die away higher up. I am 

 quite prepared to admit that this arrangement for the sense 

 of hearing might prove most imperfect for our purpose ; it 

 might nevertheless suffice for the wants of a spider. These 

 waving hairs are undoubtedly sensitive to undulations of the 

 atmosphere which are imperceptible to us, the least move- 

 ment of the air putting them in motion, and it may be that 

 very quick vibrations, such as we recognize as sounds easily 

 to be distinguished from each other, are confusion to the 

 spider. This part of our subject wants a few careful experi- 

 ments, and 1 may just mention that there is a group of these 

 peculiar hairs on the flea ; 1 have also some indistinct recol- 

 lection of having seen them upon some other insect. With 

 the legs of a spider, which are most sensitive organs of 

 feeling, if they do not also embrace those of hearing, we 

 complete our notice of the principal parts of the cephalo- 

 thorax, — Extract from a Lecture hy the late Richard Beck, 

 delivered at the Friends' Institute, London, Feb. 20, 1866. 



Proceedings of the Entomological Society of London. 



January 7, 18G7, — Sir John Lubbock, Bart., President, in 

 the chair. 



Mr. S. A. Davis, of 4, Durham-place West, Holloway, was 

 elected an Annual Subscriber. 



Mr. Westwood exhibited a number of butterflies, chiefly 

 Heliconiidaj, collected by Dr. Burchell in Central South 

 Amei'ica. 



Mr. M'Lachlan asked the reason why humming-bird hawk- 



