352 



THE MECHANICAL FUNCTIONS. 



the right and to the left. The velocity with 

 which these insects move through the air in 

 general much exceeds that of a bird, if estimated 

 with reference to the comparative size of these 

 animals.* 



* I have been favoured by Mr. George Newport with the fol- 

 lowing account of the structure of the sting of the Wild Bee, 

 (Anthophora retusa, Kirby) which he has lately carefully exa- 

 mined, and from whose drawings of the dissected parts the 

 annexed figures (163) have been engraved. " The sting of the 

 bee, A, is formed of two portions placed laterally together, but 

 capable of being separated. The point, p, is directed a little 



upwards, and is a little curved : 

 the barbs, seen still more highly 

 magnified at q, are about six in 

 number, and are placed on the 

 under surface, and their points 

 directed backwards. At the 

 base of the sting, e, there is 

 a semicircular dilatation appa- 

 rently intended to prevent the 

 instrument from being thrust 

 too far out of the sheath (seen 

 separately at v), in which it 

 moves: it has also a long ten- 

 don to which the muscles are 

 attached. It is between these 

 plates, when approximated, that 

 the poison flows from the orifice 

 of the somewhat dilated extre- 

 mity of the poison duct, d, 

 which comes from the anterior 

 part of the poison bag, b. This 

 bag is of an oval shape, and 

 is not the organ which secretes 

 the poison, but merely a receptacle for containing it: for it is 



a 



