EXPERIMENTS IM HYBRIDIZATION AND TEMPERATURE. 167 



the fore wings, in the exact position that they still occupy in 

 V. urticce and V. c-alhum, and other related species. 



(b) Forms which possibly indicate the future line of develop- 

 ment of the species. These would then be true progressive 

 forms. They are characterised by their departing still further 

 from the ancient genetic type, and from related species. In most 

 of the species of Vanessa from northern sources hitherto experi- 

 mented with, these forms are usually obtained by warmth, 

 especially with V. aniiopa. Only the species of southern source, 

 V. cardui, L., and V. atalanta, L., produced them with cold. 



(To be continued.) 



size of the black markings, as well as intermediate forms, altogether thirty- 

 four specimens. This form was much rarer in the males (seven specimens), 

 and not nearly so extreme as the females (twenty-seven specimens). One of 

 the females is shown PL I. fig. 5. This type, Staudinger's ab. canteneri, is 

 of rare occurrence in South Spain (Andalusia) and North Africa. The ab. 

 canteneri was not at all rare in pupae from Malaga, but I never had them in 

 anything like the numbers that I obtained from the pupae from Portugal, 

 with which I made this experiment, and then mostly when the insects 

 emerged without any treatment during the autumn (September and com- 

 mencement of October) before hybernation. 



No ab. canteneri were obtained from the Portugal pupae treated in the 

 usual manner. 



Four hundred specimens of Thais x>olyxena, Schiff., from Vienna, 

 treated for this warmth experiment, produced under + 37° C, in eight to 

 twelve days, twenty-six specimens of ab. ochracea, Stgr., the analogous form 

 to ab. canteneri, and a fair number of intermediates. A collateral tendency to 

 an increase in the dark markings was not manifested, but a preponderance 

 in numbers and extremity of variation in the iemales (sixteen specimens) to 

 males (ten specimens) ; PI. I. fig. 6, shows us one of these experimentally 

 browned males. I have never yet seen or bred specimens from Vienna, 

 which are as dark as the most extreme form obtained in the experiment, and 

 occasionally, under ordinary treatment in large numbers, forms nearly 

 approaching in density of marking, from Budapest pupae and from the neigh- 

 bourhood of Mehadia. 



The most extreme form obtained by the experiment approaches very 

 nearly Thais 2^olyxena var. polymnia, Mill, aberratio {cf. Milliere, Lepi- 

 dopterologie, septieme fascicule, 1881, pp. 2-4, pi. x. fig. 5) which comes from 

 the island of Euboea, and is perhaps the most extreme form of ab. ochracea, 

 Stgr., as yet known. 



The results obtained by these warmth experiments with these three 

 Thais species are that under similar treatment more or less similar develop- 

 ments are obtained, to which the female sex, both in nv;mber of specimens 

 and intensity of variation, are almost exclusively subject, leads one to the 

 supposition that this is a case of retrogression. 



As to the fact that a lighter or darker tone of brown as ground colour is 

 common to many families as well as Rhopalocera, refer to the work of Alf. G. 

 Mayer, " On the Color and Color Patterns of Moths and Butterflies " (' Pro- 

 ceedings ' of the Boston Society of Natural History, Boston, vol. xxvii. 1879). 



