2. Species frequently Melanochroic, but often not so. 

 B. Leucochroic species. 



1. Species of which all or a majority of the individuals are 



paler than in the South. 



2. Species frequentl}' paler, but not invariably so. 



Like Mr.Birchall, Dr. White believes that "natural selection" is 

 the chief cause of this variation, although meteorological influences 

 may have led to the first production of the melanochroism. 



The permanentl}^ dimorphic condition of various insects has 

 been long known. Vanessa prorsa and levana, Lycsena amyntula 

 and polysperchon, and Anthocharis belia and ausonia, have been 

 satisfactorily determined to be respectively the summer and 

 winter forms of three species. Dr. Weismann entered into and 

 extended this subject amongst the Pierides in his ' Studien zur 

 descendenz Theorie' (vol. i.), and we have recently received an 

 account of a series of experiments on Papilio Ajax and its 

 supposed allied species, Walshii, Marcellus, and Telamonides, by 

 Mr. W. H. Edwards, which appears to confirm Dr. Weismann's 

 views that the cold of winter modifies the broods produced in the 

 autumn, developing markings which have been regarded as 

 characteristic of distinct species. 



A curious instance of the modification of specific characters in 

 a species occurring in an American locust — Tragocephala Virgin- 

 iana, Fahr., (Gryllus, v.) viridifasciatus, De Geer, and Locusta 

 infuscata, Harris — is given by Mr. S. IT. Scudder (Proc. Boston 

 Soc. xvii, p. 481), in which, in addition to permanent variations 

 of colour in the specimens from New England, Texas, and 

 Florida, variations are tabulated in the antennae, fastigium of the 

 vertex, pale spots in the tegmina of the males, and cloudiness of 

 the wings. 



A memoir with figures on the " mimicry " exhibited by the 

 species of the genus Leptalis as compared with other Pieridae, by 

 Fritz Mliller, appears in the ' Jenaische Zeitschrift fiir Naturwis- 

 senschaft,' 10th Band, neue folge, 3rd Band., Heft 1, 187G. 



Geographical Distribution. 



The geographical distribution of insects is a subject which is 



attracting increased attention, and to which additional interest is 



attached since the publication of Mr. A. P. Wallace's work, ' The 



Geographical Distribution of Animals, with a Study of the 



