0)1 eoloiir relation. 237 



of Descent,' vol. i.), Mr. Poulton made various observa- 

 tions on this species and others of the genus (Trans. 

 Ent. Soc. Lond., 1884, Part. I. ; 1885, Part II. ; 1886, 

 Part II. ; and 1887, Part III.), and his latest conclusion 

 was that the spots in S. tilice probably arose from a 

 modification of a normal coloured border to the oblique 

 stripes, hence that we have in S. tili(e "a fading away 

 of the character {i.e., coloured borders) instead of its 

 origin." 



Unfortunately nineteen of the larvfe sent me by Mr. 

 Perkins were injured in the transit by post, and only 

 four were reared ; but all these were spotted. I watched 

 their development very closely, and recorded every 

 change however slight. My observations did not agree 

 in all points with the descriptions of the young larvte 

 given by Prof. Weismanu (' Studies in the Theory of 

 Descent,' vol. i., p. 233). This may have been due to 

 variability in the larvfe ; yet certain appearances, either 

 not mentioned by him, or mentioned as occurring at 

 different periods, were found in each of my larvfe ; and, 

 as some were transitory, it is possible they mav have 

 been overlooked by him, especially as his descriptions 

 are not very detailed. 



The following is a record of the appearance of the 

 larv8e day by day : — 



July 30th. — I received from Mr. Perkins twenty-three 

 larvfe of S. tilice just out of the eggs ; they were placed 

 in cylinder 15, and fed on elm. Nineteen were injured 

 in transit and were dying or dead. The larvae were green 

 all over, and the caudal horn was very long and dark 

 violet in colour. No oblique stripes. The dorsal vessel 

 showed through the skin. 



Aug. 4th. — Only four larvae were living; tbese con- 

 tinued healthy. The first ecdysis of the first larva 

 occurred. It now became light green, with the caudal 

 horn pure green. (This stage is described by Prof. 

 Weismann as occurring before first ecdysis, and before 

 the horn becomes violet). The oblique stripes were now 

 faintly discernible, and were green like the ground-colour, 

 only of a more yellowish shade. There was no trace of 

 a subdorsal line as described by Professor Weismann. 

 Length of larva before ecdysis 6 mm. The dorsal vessel 

 still showed through ; Prof. Weismann describes this as 

 appearing now for the first time. 



