Biology of the Membracidae of the Cayuga Lake Basin 419 



blend with those of the leaves and bark of the host plants to an extent 

 which offers excellent protection. The shapes, even of the local forms 

 which are of course far less bizarre than the grotesque exotic species, 

 are of an interesting variety and present opportunities for a wide range 

 of surmises. It has been noted in the discussion of the pronotal anatomy 

 (page 312) that many explanations have been offered for the unusual 

 structures shown m the exoskeleton of this famil}'^, and that the theories 

 both of natural selection and of orthogenesis may be well illustrated 

 l)y certain forms of Membracidae. An elaboration of this subject would 

 be out of place in a study lunited to the forms of the Cayuga Lake Basin, 

 since for an appreciation of the subject the entire family must be taken 

 into consideration. Nevertheless it may be pertment to call attention 

 to a few of the local species which offer rather peculiar features apparently 

 adapted for imitation or protection. 



It has been remarked that the nymphs of Thelia himaculata and Van- 

 duzea arquata are almost indistinguishable when at rest in cracks of bark. 

 This is due not only to their color but also to the dorsal protuberances, 

 which closel}^ resemble the irregularities of the plant. An even more 

 strildng instance is offered by the nymphs of Enchenopa binotata, the 

 dorsal spines of which are wonderfully like the tiny unfolding leaves of 

 the locust which are contemporary with them, even the light green color 

 being common to both. In the mature insect the adult of Thelia himaculata 

 shows a pronotal projection which is easily mistaken for the thorns of 

 the host plant, and m the adult of Enchenopa binotata the pronotal horn 

 in the same manner imitates the spmes and stipules of the locust. This 

 certainly seems to be an adaptation which may be accounted for by natural 

 selection. Poulton (1903:277) has called attention to the fact that it 

 is hard to deny the theory of protective resemblance when the same 

 object is accomplished by both the nymph and the adult but in different 

 ways. In the case of the local forms mentioned above, the nymph imitates 

 the micurling leaf or the irregular bark by spines on both thorax and 

 abdomen — chiefly the latter — while the adult imitates an entirely 

 different part of the plant by the development of an entirely different 

 part of the body. On the other hand, some of the commonest of the 

 local species of Membracidae m no respect seem to resemble any part 

 of the host on which they live, altho their shapes are decidedly peculiar. 

 The high dorsal crest of the Telamonas, for example, can only by a stretch 



