PS re HE. 



49 



be altered by temperatures which are 

 the reverse of the normal ones to which 

 the pupae would be subjected in nature. 

 Cold IS only the initiatory stimulus for 

 the levana tendency, and heat for the 

 prorsa tendency. An example of adap- 

 tive seasonal-dimorphism i?iay be af- 

 forded by Va?iessa levana-prorsa where 

 the summer form prorsa may gain some 

 advantage by its general resemblance 

 to Limenitls sibyl la ^md catnilla ; 

 while it is possible that the overwin- 

 tered form, levana, mav gain some 

 advantage from its resemblance to the 

 dead leaves of the spring woods. 



We shall now describe a few more 

 experiments the bearing of which will 

 become apparent when we discuss the 

 results of the researches. 



In 1S75, '77, '80, Edwards performed 

 some interesting temperature experi- 

 ments upon Papilio ajax. There are 

 four generations of Papilio ajax in 

 West Virginia, three being summer 

 generations, and one which winters 

 over in the chrysalis state, and may pro- 

 duce two distinct forms of butterflies, 

 walshii and telamonides. The summer 

 generations are all alike and belong to 

 the form niarcellus. The eggs laid by 

 the spring forms usually change into 

 pupae from which the summer form, 

 marcellus, emerges ; some of these 

 pupae, however, winter over and pro- 

 duce walshii or telamonides the follow- 

 ing spring. 



Edwards subjected the pupae reared 

 from eggs laid by captive females of 

 walshii or telamonides, to the cold of an 

 ice house for periods varying from 11 



days to 2 months. These pupae would 

 normally have produced only marcellus, 

 but owing to the influence of the cold, 

 the majority of them gave rise to butter- 

 flies colored like telamonides. A few, 

 however, defied the cold and remained 

 marcellus, and still fewer were con- 

 verted into the coloration of walshii. 

 Edwards also tried the reverse experi- 

 ment, that is he subjected the over-win- 

 tering chrysalids to the heat of a green 

 house, but they gave rise to telamonides 

 and walshii just as they normallv would 

 had thev been exposed to the winter's 

 cold. 



But by far the most remarkable exper- 

 iments upon the effects of temperature 

 which have been performed thus far, are 

 those of Fischer ('95) upon Vanessa 

 antiopa. When the pupae of this form 

 are placed upon ice at 0-1° C. the but- 

 terfly is greatly modified. The ground 

 color is a darker velvet brown than in 

 the normal antiopa, and the blue spots 

 are greatlv enlarged, and changed into 

 an intense violet-blue. Fischer de- 

 scribes this form in the " Gubener ento- 

 mologischer Zeitschrift as V. antiopa 

 arteiiiis. A temperature of 35° C, 

 however, produces a form which is 

 exactl_v the opposite of that produced 

 bv cold. Fischer describes it In the 

 " Gubener entomologischer Zeitschrift, 

 July 1S94" as V. an/iopa, aberratio 

 epione. The ground color is lighter 

 than the normal, and the blue spots 

 much reduced in size. But the most 

 astonishing result obtained by Fischer 

 came from experiments with abnormally 

 high temperatures. He subjected fresh 



