DISTRIBUTE INSECT VARIETY. 275 



southivard [!') from the centre of distribution, we witness the 

 species producing fewer annual broods, and these varieties often 

 supplanting the type. Thus the butterfly Araschnia Prorsa, 

 common on the Continent in marshy Avoodland, produces three 

 annual broods. The individuals of the first, that come out in 

 Ajml, are of a variety Levana (Frontispiece, Fig. 1.), which is 

 above of a fulvous colour with black spots, while the summer 

 dress is black, with a red line (Fg. 2) . This wonderful disparity 

 may be nevertheless resolved as a phase of sestival melanism, 

 where the black spots of the early brood have run together into 

 lines, and an excess of summer ink blotted over the wings. We 

 see all the markings destined to enliven the warmer season as in 

 a Chinese puzzle sketched out on the orange wings of spring, and 

 the change in character of secretion, due to heat it may be 

 presumed, and less duration in the chrysalis state, has served 

 alone to expand the pattern and mark it in with black and white. 

 Beneath, from similar cause, we find yellow has become white or 

 brown, as the case may be. Dr. Staudinger, to further establish 

 the matter instituted an experiment, and by placing the chrysalides 

 of the April disclosure in an ice-box, found that an intermediate 

 form, porina, rare in a state of nature, resulted. 



Other examples of season metamorphism have been discovered. 

 The spring brood of the cabbage butterflies Fieris rapcB and Napi 

 in the Northern Hemisphere is of a purer white than the summer 

 varieties, with the blackish markings more or less obsolete ; 

 and pupae of the summer generation of Napi kept in an ice-house 

 produce an October brood with the winter dress. The North 

 American Swallow Tail {Papilio Ajax) has three varieties. The 

 first two appear successively in spring from over- wintering pupa?, 

 while the last appears in summer in three generations. In this 

 case Mr. Edwards found hy application of cold, the May cater- 

 pillars of the earliest form reproduced the same variety in 

 August, while those which emerged later on were of the summer 

 variety. Another butterfly {Pi/ciodes- Tharos) is likewise stated 

 to be polymorphic, and in the Catskills digoneutic, or with two 

 annual generations, the first of which is always of a winter type ; 

 but at Coalburgh this butterfly produces two more annual genera- 

 tions. A fourth generation produced in exceptional Canadian 

 seasons exhibits the two forms. On the coast of Labrador, again, 

 s 2 



