166 THE ENTOMOLOGIST. 



(a.) Forms which belong to the former history of the species — 

 that is, true retrogressive forms. They can be recognised at 

 once by their approaching in markings to related species or 

 forms which are recognised as nearer the original type of the 

 genus. 



V. polychloros, L., for example, by the application of cold, 

 obtained a row of blue spots on the outer margin of the upper 

 side of the fore wings, which are usually wanting, but which are 

 still present in the nearly related V. uriica, L. ; and V. io also 

 approached V. urticce both on the upper and under sides. F. 

 antioioa obtained quite noticeably two spots on the upper side of 



Another fact which shows the effect that low temperature has had on 

 P. hospiton is that it has only one generation during the year, whereas 

 P. machaon in nearly the whole of its widely extended area has two genera- 

 tions yearly. 



Up till now I have bred 583 specimens of P. Jiosjnton, but only during 

 the abnormally hot year 189S did I obtain a few specimens during the month 

 of August from fresh pupae from Sardinia before hybernation. These are 

 intermediate between the ordinary forni and the forms obtained by the 

 experiment. 



The results obtained by warmth in changing the three Thais species and 

 their local forms — cerisyi, B., var. deyrollei, Obthr., rumina, L., 2>olyxena, 

 Schiff. — are worth noting. 



One hundred and fifty pupae of the local form of T. cerisyi, B., from 

 Amasia, var. deyrollei, Obthr., were subjected in February for nine to fifteen 

 days to a constant temperature of -1- 37° C. until emez'gence. About one-third 

 of the female specimens obtained a brownish coloration of the ground colour 

 of both wings on the upper sides in place of the white tone and a weak dis- 

 coloration of the under sides, mostly accompanied by an increase in size of 

 the black markmgs. This form is rarely obtained in ordinary circumstances. 

 The most extreme forms reached on the upper side, the brown-yellow of 

 typical rumina ab. cayiteneri, Stgr., from Malaga. PI. I. Sg. 2 shows one of 

 these dark brown female specimens obtained by this experiment, but the 

 black markings are only increased somewhat on the fore wings. 



In the male specimens obtained by the same treatment a noticeable 

 darkening of the light ground colour was only exceptionally present, but 

 nearly always, though not to any extent, there was a slight increase in the 

 size and number of the black markings, at times accompanied by an enlarge- 

 ment of the red spots of the hind wings. 



The male (PI. I. fig. 3) shows these characters. Its markings thus attain 

 a growing resemblance to the light female forms of Thais var, deyrollei, 

 Obthr., which occur regularly at Aintab, north-east of Antioch (Syria). We 

 concluded (Standfuss, Handb. d. palaearct, Gross-schm, 1896, pp. 226, 227) 

 that these female types from Aintab were the most progressive, because they 

 were the nearest approach to the male type of coloration ; and those retro- 

 gressive males procured fi'om the Amasia pupae by warmth are a still nearer 

 link to the above-mentioned female Aintab tj'pes. A female from Aintab is 

 shown (PL I. fig. 4) whose pupa has not been experimented with. 



A few male specimens obtained by the experiment a very curious addi- 

 tion to their wing-structure, a portion of the hind wings with the three long 

 tails being lengthened : so that there was a certain resemblance to the type 

 of hind wings of certain Pajnlio s-pecies— P. podalirius, L., for example. 



Ninety-three pupae of Thais rumina from Portugal produced, under a 

 temperature of + 37° C. after hybernation during January and February in 

 six to fifteen days, a similarly dark brown type, mostly with an increase of 



