in] MOUTH-PARTS AND SENSE-ORGANS 47 



(1664). Robert Hooke (16351703) was a somewhat 

 eccentric and irritable man of science who acted as 

 secretary to the Royal Society. His labours were too 

 varied to be effective. He nearly discovered the laws 

 of gravity and also studied fleas. To him belongs 

 the credit of having detected the antennal groove. 

 Just as many of the older naturalists thought that 



Fig. 5. The antenna of a flea. A, concealed in the groove. B, pro- 

 truded from the head. The versatile basal segments and the 

 terminal club, in this case with segments on one side of it, 

 should be noticed. 



the maxillary palpi were antennae, so others thought 

 that the antennae of a flea were its ears. And when, 

 with the help of their lenses, they saw the antennae 

 erected and protruded from their grooves, they 

 imagined that the insect was cocking its ears and 

 listening after the manner of a horse or ass. But 

 the antennae of fleas are much more to them than 



