On the Pygidia and Cerci of Insects. By Henry Davis. '255 



motile hairs, forming organs of feeling induced by the move- 

 ment of the air in their neighbourhood ; not, perhaps, an organ 

 of a new sense between touch and hearing, but of feeling not 

 excited in the ordinary way by actual touch. I apprehend that any 

 insect having pygidia must infallibly be warned of the approach, 

 however stealthy, of an enemy ; even if, from its position behind 

 the insect, that enemy could not be seen, the warning being given 

 by the moving hairs actuated by the disturbance of the surrounding 

 air. 



In these notes I think may be found reasons for discarding the 

 use of the word " cerci," as applied to all those insect organs which 

 are plainly modified forms of the better known "pygidia." The 

 latter simply meaning something on the iiropigium, will permit them 

 to be of any form or size ; and as '' cerci " means tails, it is absurd 

 to apply it to objects of no length, as the pygidia of Chrysopa 

 and Pulex. But if these be tails, then indeed man himself has one. 



