iv VANESSA PRORSA AND VANESSA LEVANA 117 



of new species; for the transition from one form to the 

 other is sudden and immediate, inasmuch as not one but 

 several new characters separate the one from the other. 



The original form is obviously the Levana, which approxi- 

 mates in colour and markings to related species of Vanessa, 

 especially to Vanessa polychloros and c. album. The summer 

 form, Prorsa, shows nothing of this marking ; it has on the 

 two black wings a transverse row of light spots, and on the 

 anterior wing in addition to this row some white dots ; its 

 whole marking appears to connect it very closely with the 

 genus Limenitis. 



If in the whole habitat of Vanessa Prorsa such climatic 

 changes were to take place that the form produced by cold 

 were no longer developed, then the Prorsa would alone remain 

 as a new species, which would be classed according to its mark- 

 ing rather among the species of Limenitis than among the 

 species of Vanessa above named, or would in any case take 

 a position completely separate from the latter. 



Weismann has himself attempted to prove that their colour- 

 ing is not protective to butterflies during their flight, " because 

 the colour of the background against which they are seen is 

 continually changing, and because' their fluttering movement 

 would betray them to their enemies in spite of the most com- 

 plete adaptation to the background." He declared, on the 

 basis of his own observations, that butterflies are most liable 

 to be seized by their enemies when at rest with their wings 

 folded together, and especially at night ; in the latter case, 

 mostly by spiders. For this reason butterflies so often have 

 colourings and markings on the underside of their wings 

 which mimic the surface on which they settle. 



In fact, who has not, in the attempt to catch butterflies, 

 met with the experience that the insect suddenly vanished 

 from his sight ? It had settled somewhere, and even with 

 the keenest sight could no more be found. Even the common 



