172 Studies in the Theory of Descent. 



so rich in information as the Sphingidce, or, as I 

 am inclined to believe, the Papilionidce, since all 

 families of caterpillars do not possess such a 

 marked and diversified pattern, nor do they present 

 such a varied and characteristic bodily form. The 

 representation of the true, i. e., the blood-relation- 

 ship, and through this the formation of natural 

 groups with any completeness, can certainly only 

 be looked for when we are intimately acquainted 

 with the different stages of development of the 

 larvae of numerous species in every group, from 

 their emergence from the egg to their period of 

 pupation. The genealogical relationship of many 

 forms at present of doubtful systematic position 

 would then be made clear. This investigation, 

 however, could not be the work of a single indi- 

 vidual ; not only because the materials for observa- 

 tion are too great, but, above all, because they are 

 spread over too wide a field. It is not sufficient 

 to study the European types only we should 

 endeavour to learn as much as possible of the 

 Lepidoptera of the whole world. But such obser- 

 vations can only be made on the spot. Why 

 should it not be possible to trace the development 

 from the egg, even under a tropical sky, and to 

 devote to breeding and observing, a portion of that 

 time which is generally spent in mere collecting ? 

 I may perhaps be able to convince some cf the 

 many excellent and careful observers among ento- 

 mologists, that beyond the necessary and valuable 



