184 Studies in the Theory of Descent. 



stage, viz. the small dots which appear in pairs 

 near the posterior edge of segments 5 n. 

 These dots cannot have been developed from 

 the subdorsal line, as they are situated higher 

 than the latter. Their colour varies according to 

 the ground-colour of the caterpillar, but it is always 

 lighter, being light-green in green specimens, 

 dull yellow in those that are light brown, and 

 grey in the blackish-brown caterpillars. These 

 " dorsal spots," as I shall term them, are chiefly 

 of interest because they are present in Chcero- 

 campa Porcellus, in which species they appear one 

 stage earlier than in C. Elpenor. 



CH^ROCAMPA PORCELLUS, LINN. 



Females captured on the wing, laid in the breed- 

 ing-cage single eggs of a light green colour, 

 spheroidal in form, and very similar to those of 

 C. Elpenor. 



First Stage. 



The caterpillars on first hatching measure 3.5 

 millimeters in length, and are of a uniform light 

 green colour, with a fine white transverse line on 

 the posterior edge of each segment, precisely 

 similar to that which appears in the second stage 

 of C. Elpenor. They resemble the latter species 

 still further in showing a fine white subdorsal 

 line, which can 'easily be recognized by the naked 

 eye (Fig. 24). Although the adult larva is 



