The Influence of External Conditions 25 
whose growth occurs in late autumn (with lower temperature 
and decreasing vegetation) and is completed’in the autumn so 
that they winter as pup, are generally smaller in the first gen- 
eration and larger in the second or summer generation; for 
the caterpillars of the latter are born in summer and have plenty 
to eat. Conversely, species which winter over as small cater- 
pillars and develop further during the favorable conditions of 
spring produce larger butterflies in the first than in the second 
generation. 
LITERATURE, CHAPTER II 
BACHMETJEW, P. Ueber die Temperatur der Insecten nach Beobachtun- 
gen in Bulgarien. Zeit. f. wissen. Zool. LXVI. 1899. 
Der kritische Punkt der Insecten und das Entstehen von Schmetter- 
lings-aberration. Ill. Zeit. f. Entomol. V. 1900. 
Experimentelle entomologische Studien. 1x. Band. Temperaturver- 
haltnisse bei Insecten. Leipzig. gor. 
Kalometrische Messungen an Schmetterlingspuppen. Zeit. f. wissen. 
Zool. LXXI. 1902. 
Bateson, W. On Variation in the Colour of Cocoons of Eriogaster 
Trans. Entomol. Soc. London. 1892. 
On Variation in the Colour of Cocoons, Pupe, and Larve; Further 
Experiments. Ibid. 1892. 
Brucke, E. Ueber den Farbenwechsel der Chamaeleonen. Sitz. Kais. 
Akad. Wiss. Wien, math.-naturw. Cl. VII. 185r. 
Untersuchungen ueber den Farbenwechsel des Afrikanischen Chami- 
leons. Denkschr. Kais. Akad. Wiss. Wien, math.-naturw. Cl. IV. 
1852. 
Caron F.C. The Colour Changes in the Skin of the so-called Florida 
Chameleon, Anolis Carolinensis Cuv. Proc. of the Amer. Acad. of 
Arts and Sci. XXXIX. 1903. 
CHLopKovsky, N. Sur quelques Variations Artificielles du Papillon de 
lOrtie (Vanessa urtice). Ann. Soc. Entomol. de France, LXX. 
Igol. 
DIXxEy, F. A. On the Phylogenetic Significance of the Wing marking in 
certain Genera of the Nymphalida. Trans. Entomol. Soc. Lon- 
don. 1891. 
Mr. Merrifield’s Experiments in Temperature-Variation as Bearing 
on the Theory of Heredity. Trans. Entomol. Soc. London. 1894. 
DorFrMEIsTEeR, G. Ueber die Einwirkung verschiedener wihrend der Ent- 
wickelungsperiode angewandter Warmegrade auf die Farbung und 
Zeichnung der Schmetterlinge. Mitt. d. naturw. Ver Steiermark. 
II. 1864. 
Ueber den Pinfluss der temperatur bei der Erzeugung von Schmetter- 
linge varietéten. Ibid. 1879. 
Epwarps, W. H. An Abstract of Weismann’s paper on “The Season 
Dimorphism” of butterflies, to which is appended a statement of 
