O. A. Merritt Hawkes Idi 



Summary. 



1. The plain or non-spotted condition of the larva of P. ricini is 

 recessive to the spotted condition of the larva of P. cijnthin (Ning-po 

 variety). 



2. The dominance in the F^ generation is incomplete ; all the larvae 

 are spotted but not all have the full complement of spots. 



3. The spots are probably represented, not by one, but by a group 

 of related gens in the chromosome. 



4. The dominant homozygous and the heterozygous forms can be 

 distinguished only by breeding, as both may be either full- or partly- 

 spotted. 



5. A number of abnormal larvae with reduced tubercles occurred 

 in the F.2 generation ; when mated with normal larvae, this character 

 behaved as a recessive; whether it was a mutation which occurred de 

 novo as a result of this particular cro.ss or whether it is a result always 

 to be expected from this hybrid, has not yet been determined. This non- 

 tubercled mutation (?) is interesting in relation to the few non-tubercled 

 species among the Saturniids. 



EXPLANATION OF PLATE VIII. 



Figures A 1, A 2, A 3, A 4 are larvae of J''2- 



Al — 4 natural size. Normal tubercles. Full spots (i'). 



A 2 — f natural size. No trace of tubercles. Full spots (S). 



A3 — I natural size. Irregular tubercles. Full spots (S). 



A 4 — A uatural size. Slight vestiges of tubercles. Reduced spots (RS). 



Figures B 1, B 2 are larvae of Fi and F,, of the cross between a normal and an abnormal 

 larva. (See Table III.) 



B 1. — Natural size. Normal tubercles. Full spots (.S'). 



B 2. — Uppei- larva— i natural size. Traces of tubercles as chitinous rings. No spots (F). 

 Lower larva — i natural size. Normal tubercles. No spots (F). 

 Figures C 1, C 2, C3, C4 arelaivae of 2' a- They were blown by Mr J. W.Watson. J natural 

 size. 



C 1, C 2 are lateral and dorsal views of a non-tubercled, full-spotted larva (S). 

 C 3, C 4 are lateral and dorsal views of a tubercled, plain (P) larva. This specimen 

 shows some spots of the lower later. il series on the abdominal legs. . The large 

 spots at the side are the spiracles. 



