164 Studies in the Theory of Descent. 



phyletic development, because they make us ac- 

 quainted with the markings of the progenitors of 

 the existing species. For these investigations it 

 is therefore in the first place necessary to obtain 

 fertile eggs. Female Sphingidce, however, do not 

 generally lay eggs in confinement, 1 or at most 

 only a very small number. In the case of many 

 species (Deilephila Galii, D. Lineata^ D. Vesper- 

 tiliO) D. Hippophaes) I have for this reason un- 

 fortunately been unable to observe the entire 

 development, and such observations would in all 

 probability have given especially valuable infor- 

 mation. 



I was certainly successful in finding the young 

 larvae of some of the above as well as of other 

 species on their food-plants, but even in the most 

 favourable instances only individuals of the second 

 stage and generally older. When, however, not- 

 withstanding this imperfection of the materials, 

 and in spite of the important gaps thus inevitably 

 caused in these series of observations, it has 

 nevertheless been possible to form a picture, on 

 the whole tolerably complete, of the phyletic de- 

 velopment of the Sphinx-markings, this well indi- 



1 Only the species of Smerinthus can be made to lay eggs 

 regularly in confinement ; Macroglossa Stellatarum laid a num- 

 ber in a large gauze-covered breeding-cage; the species of 

 Deilephila could not be induced to lay more than single ones 

 in such a cage. From species of Charocampa also I never 

 obtained but a few eggs, and from Sphinx and Acherontia never 

 more than single ones. 



