1890.] ENTOMOLOGICAL NEWS. 5 



prevalent In the mountains and to the north, while blue is a south- 

 ern characteristic. This, however, is not an invariable rule. In 

 H. ignita there is a regular geographical sequence southward from 

 golden through green to blue. The cupreous and greenish varie- 

 ties of H. chalybea mentioned by Dr. Horn I regard as atavisms. 



Here, though, it becomes necessary to define one's notion of 

 atavism. Commonly, it is said to be reversion to the state of an 

 ancient progenitor. Some confine it to the development of half- 

 forgotten rudiments, but to me this seems an unwise restriction. 

 To me there are two fundamentally different kinds of atavism : 



(i) Due to the development of structures now obsolete. 



(2) Due to arrest of development and consequent resemblance 

 to a less-developed or differentiated ancestor. 



The first class is due to abnormal developm.ent, the second to 

 abnormal arrest of developmeyit — two very different things. Our 

 atavistic green Haltica chalybea clearly belongs to the second 

 division. The first di\dsion is exemplified in a horse that develops 

 extra toes. 



Mr. T. H. Hall gives me a list of his varieties of Donacia 

 sericea. The females are coppery, brassy and green. The males 

 are green, violet and purple. Here we see in the female the older 

 type of coloration to what obtains in some butterflies and other 

 insects. 



At Chislehurst, in England, I collected two species of metallic 

 Chrysomelce. C. gcettingensis, which lived concealed at the roots 

 of herbage, was dark blue. C. hypericin on Hypericum, and 

 more exposed, is green. Here seems protective adaptation to 

 circumstances ; or perhaps we may say that C. hyperici would 

 have developed in time to blue, but natural selection prevented it. 

 C. gcettingensis has beautifully pink wings, but these need not be 

 considered in the present connection. 



Dr. Hamilton found a variety of Calosoma wilcoxi, varying 

 from its normal green and golden to purple-black, with the mar- 

 gins of thorax and elytra purple-blue. Possibly this was a token 

 of the future color of C. ivilcoxi. In Carabus we have C. nitens 

 with something the color of Cal. wilcoxi, and the coloring of 

 Dr. Hamilton's variety is a permanent institution in C. violaceus. 

 A. Berge found he could actually manipulate these color changes 

 in Cam^^^i- by chemical means, and produce certain "varieties" 

 at will. 



