MELANISM AND MELANOCHROISM. 77 



in the young larva and in the mniicis attitude of the older 

 larva, and in these respects are to some extent intermediate 

 between Viininia and Cuspidia, depart from 'the types of both 

 groups in being colourless. It may be that they are the more 

 ancient forms and that the colouring of the others has been 

 acquired later. 



It may be useful to append a note of the sizes of these eggs 

 and the number of their ribs, both items being subject to 

 variation within small limits. 



Number of ribs. 



tridens 38 



strigosa 41 



leporina 41 



alni 53 



P^i ■• 54 



megacephala 66 



aceris 75 



ligustri 60 



or ion 30 



caruleocephala 13 



coryli 25 



The Acronyctas are so flat that the measurement of their 

 height is difficult. In most it is about half the diameter, less 

 than this in megacepJiala and perhaps in leporina. 



DESCRIPTION OF PLATE VIII. 

 Fig. I. — Egg oi Acronycta {Cuspidia) psi, vertical view of upper surface X 25 diam. 

 Fig. 2. — , , , , , , tridens X 26 diam. 



Fig. 3. — ,, ,, ,, leporina X 22 diam. 



Fig. 4. — ,, ., ,, aceris X 27 diam. 



Fig. 5. — ,, ,, ,, megacephala x 19 diam. 



Fig. 6. — ,, ,, ,, alni x 25 diam. 



Fig. 7. — ,, ,, ,, strigosa X 29 diam. 



Fig. 8. — ,, ,, (Bisulcia) ligustri X 27 diam. 



Fig. 8a. — ,, ,, ,, ,, side view. 



Fig. 9. — ,, /?^Wfl5 r;?;^/? upper surface X 29 diam. 

 Fig. 9a. — ,, ,, ,, side view. 

 Fig. 10.— ,, Moina orioii upper surface X 34 diam. 

 Fig. loa. — ,, ,, ,, side view. 



Fig. II. — „ D. caruleocep/iala upper surface x 26 diam. 



Fig. iia. — „ ,, ,, ,, as naturally covered by maternal scales. 



Fig. lib. — ,, „ side view. 



( To be continued.) 



MELANISM AND MELANOCHROISM IN BRITISH 

 LEPIDOPTERA. 



By J. W. TUTT, F.E.S. 

 {Continued from page 53.) 



I HAVE previously noted that other views, based indirectly 

 on physiological causes, have been brought forward to ac- 

 count for melanism. With regard to these, Mr. Nicholas 

 Cooke {Entomologist^ vol. x., p. 94) writes, concerning the 



