i86 



NA TURE 



[December 23 1897 



Experiments in 1891. — The first result established in 1891 

 was that the spring emergence of S. tetralunaria could be made 

 by forcing during the penultimate pupal period to assume the 

 colouring but not the markings of the summer form. In respect 

 to the colouring it was found to be almost or quite as sensitive 

 to temperature as the summer form, but in respect to markings it 

 was completely resistent. The duration of the pupal period could 

 in no case be shortened to that of the summer form ; early and 

 continued exposure of the winter pupa to a temperature of 

 80° F. or even of 60° F. generally proved fatal. 



Experiments on the pupae of both spring and summer broods of 

 .9. Itinaria, Schiff. , and S. bilunaria, and on the spring brood of 

 Falcaria fakatai ia, L., gave the same general result of darken- 

 ing in the cooled specimens and paling in the forced ; and pre- 

 vious conclusions with regard to S. tetralunaria received con- 

 firmation. 



In the case of V. tirticcz, which was this year more completely 

 investigated, it was found that a moderately low temperature 

 generally deepened the colouring slightly, lowered the tone of 

 the yellow patches, and spread the dark portions, especially the 

 borders, enlarging also the marginal blue crescents. 



Further experiments were also tried with Lasiocainpa quercus 

 and its variety callunce. As in the former examples, exposure 

 to a temperature of 80° F. was found to cause lightening, and 

 to a temperature of 47° F. darkening, of the general ground 

 colour. In L. callimcF the effect was most pronounced in the 

 males. Some of the forced callunce would, so far as regards 

 colouring, be classed as L. quercus. Arctia caja, L., was found 

 to be a species unusually intolerant of low temperatures, many 

 pupoe dying when exposed to 50° or 60° F. In those that 

 emerged there was a tendency for the dark spots on the hind- 

 wings to spread and become confluent, and for the black trans- 

 verse abdominal bars to increase in length and breadth. At 80° 

 to 90" F. the brown of the fore- wings was paler than normal, 

 and the red of the hind-wings took on a yellower shade. 



The results obtained in this and former years seemed to Mr. 

 Merrifield to afford evidence that besides the marking and 

 coloration, the size and (less markedly) the shape of the wings 

 might be affected by temperature. In most of the species tried 

 the forced appeared to be smaller than the cooled specimens, 

 and in the three species of Selenia a lengthening and increased 

 angularity of the fore-wing seemed to result from a lowered 

 temperature. In V. urticce little difference was observed except 

 in those from pupse at 47° F., which were generally smaller 

 than the others. 



Temperature experiments on Papilio viachaon, L., P. 

 podalirius, L., (spring emergence), Thais polyxena, Schiff., 

 Argynnis paphia, L., Cerura vintila, L., Agrotis comes, Hb., 

 and Attactis cynthia, Drur. (all winter pupae), gave negative 

 results, as also did a careful trial of the possible effect of dark- 

 ness and of different coloured light on S. tetralunaria and 

 A. cynthia. 



Experiments in 1892. — The experiments made this year were 

 chiefly on butterflies ; the first species taken being Picris itapi, 

 L. Pupae of the summer brood were forced at 90° F. or kept 

 at about 67° F. These yielded perfect insects of the ordinary 

 summer form. Others of the same brood were iced for from 

 three to four months ; some were then exposed to an artificial 

 "spring" temperature of 54° F., and the rest were forced at 

 80° F. Both of these two classes showed most of the character- 

 istics of the usual spring form ; e.g. on the upper surface greater 

 suffusion and less intensity of dusky colouring ; on the under 

 surface faintness of the spots on the fore-wings and strongly 

 marked nervures on all wings, with increased strength of the 

 yellow parts. Those forced after freezing had the nervures more 

 strongly marked than the rest, but in other respects partook 

 less distinctly of the spring colouring. About one-fourth of the 

 pups resisted attempts at forcing, and "went over" to the 

 following spring, thus affording another instance of " physio- 

 logical dimorphism." 



A second species taken was Vanessa atalanta, L., which gave 

 interesting results. About icxj pupae were divided into six 

 classes, and treated as under : — 



( 1 ) 80° to 90° F. , emerging in 6 days. 



(2) About 64° F. , emerging in 18 or 19 days. 



(3) About 56° F. (equable) ; emerging in about 34 days. 



(4) 51° to 64° F. out of doors, averaging about 54" ; emerging 

 in 44 days. 



(5) 45° to 58° F. , averaging about 51° ; emerging in about 40 

 to 50 days. 



(6) 45° F. for from 32 to 47 days, then to various temperatures 

 ranging from 90° F. (emerging in 6 days more) down to a mean 

 of about 55° (emerging in from 19 to 34 days more). 



Classes 2, 3 and 4 did not greatly differ among themselves or 

 from the normal ; their coloration, however, seemed on the 

 whole to increase in intensity with the lowering of the tempera- 

 ture. In Class I the black ground-colour was slightly suffused 

 with golden brown, the scarlet band was broadened, and its in- 

 tensity of colour somewhat diminished. A new scarlet spot 

 appeared on the under surface of the fore-wing (Fig. 9). In 

 Class 5 the pale costal patch on the under surface of the hind- 

 wing became more pronounced, and showed an increased 

 tendency to spread along the costa. A light ochreous cloud 

 ai)out the middle of the hind margin of the same wing-surface, 

 visible in normal specimens, became more strongly marked. In 

 Class 6 the scarlet band was tinged with carmine, narrowed in 

 area, and broken up by transveise bars of black. There was a 

 tendency in the fore-wing to the diffusion of white and lavender 

 scales over the black ground-colour, and round the edges of the 



Fig. 7 — Ch^ysophanus phlcpas. 

 (Diagrammatic.) Korced ; 

 showing large size of black 

 spots on fore-wing, and 

 diminished breadth of copper 

 border on hind-wing. 



Fig. 8. — Chrysofiliamts fihlceas. 

 (Diagrammatic.) Iced ; show- 

 ing diminished size of black 

 mai kings, and increased 

 breadth of copper border. 

 The latter ha: lost its external 

 serrations, and shows pro- 

 longations passing inwards 

 along the nervures. 



Fig. 9. — Vanessa atalanta. 

 under side. (Diagrammatic.) 

 Forced ; shows appearance of 

 new red spot (a) between 

 scarlet band {J)) and inner 

 border of fore-wing. 



Fig. 10. — Vanessa atalanta^ 

 upper side. (Diagrammatic.) 

 Cooled ; shows scarlet band 

 (b) broken up, enlargement of 

 white costal mark (r), new 

 row of minute blue spots (d'). 

 The submarginal spots of the 

 hind-wing (c) are centred with 

 lavender. 



NO. 1469, VOL. 57] 



white spots. The submarginal black spots of the hind-wing 

 were often centred with lavender, occasionally a row of minute 

 blue spots appeared in the margin of the dark portion of the 

 hind-wing, and another on the extreme border of the wing itself 

 (Fig. 10). On the under side there was more diffusion arid 

 blurring of markings, with an increased tendency towards the 

 multiplication and spreading of pale areas. 



Chrysophanus phlceas, L. , a species which had already been 

 worked at by Weismann, was also made the subject of a series 

 of temperature experiments. Well-marked differences were 

 found to exist between the extreme forms produced under con- 

 ditions of heat or of cold. The former caused enlarged .size 

 and diminished intensity of the black spots, a narrowing of the 

 coppery band on the hind-wing, and a dusky suffusion of the 

 fore- wings, especially towards the bases (Fig. 7). Under the 

 latter, the black spots are much reduced in size, the coppery 

 parts are lighter, and the coppery band on the hind- wing broadens, 

 loses its posterior serrations, and often shows prolongations 

 along the nervures towards the base (Fig. 8). These effects are 



