14 



FIELD ZOOLOGY. 



through specialized cells Ijong just under the epidermis, 

 more abundantly scattered in some portions of the body 

 than in others. We do not feel at all just over the elbow- 

 joint, and much less feebly on the cheek than on the lips. 

 But there are other means of contact sense. Close your 

 eyes and let some friend touch one of the hairs on the 

 back of your hand or arm, and you have the immediate 



sensation of having 

 been touched. A fine 

 nerve at the base of 

 this hair communi- 

 cated to your brain the 

 stimulus of contact. 

 In this latter way, 

 insects are provided 

 abundantly with the 

 contact sense. (Fig. 5.) 

 Catch a house fly, and 

 you will find a number 

 of stiffish hairs on the 

 surface of the body. Lightly touch one of these hairs, 

 and you may be able to prove to yourself that they are 

 actually tactile hairs. Most insects have these hairs in 

 greater or less abundance . There are hairs on some insects 

 which serve other purposes, such as the stiff hairs on the 

 hind legs of some of the swimming beetles, or the auditory 

 hairs, but possibly even these are contact sense organs in 

 addition to their other use. Where the body wall of an in- 

 sect is thickly chitinized, unless the chitin armor is pierced 

 by one of these hairs, the insect seems feebly, if at all, 

 sensitive to touch. A praying mantis on the desk of the 

 author was exploring a bunch of golden-rod, and was 

 confronted by a woolly bear, one of the hairy brown cater- 



FlG. 5. — Diagram showing innervation of 

 a tactile liair. ch, chitinized cuticle; hyp, 

 cellular layer of skin; sc, ganglion cell; co 

 gangliohof central nervous system. (Kellogg, 

 after vom Rath.) 



