MELANISM AND MELANOCHROISM. 
77 
in the young larva and in the riimicis attitude of the older 
larva, and in these respects are to some extent intermediate 
between Viminia and Cu^pidia, 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. 
Diameter, mm. 
Height, \ 
tridens 
38 .... 
o-8o 
strigosa 
41 
074 
leporina 
41 
no 
alni 
53 
i-oo 
psi 
54 
0-97 
megacephala 
66 
1-23 
aceris 
75 
fio 
ligustri 
0-90 
orion 
^0 
070 
cceruleocephala 
13 
0-93 
o’6i 
coryli 
25 
076 
0*47 
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 megacephala and perhaps in leporina, 
DESCRIPTION OF PLATE VIII. 
Fig. I. — Egg of Acronycta {Ctispidia) 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. — ,, ,, ,, strLosa X 29 diam. 
Fig. 8. — ,, ,, {Bisulcia) ligustri X 27 diarn. 
Fig. 8a. — ,, ,, ,, ,, side view. 
Fig- 9- — ,, Demas coryli %vcd2.Q.& X 29 diam. 
Fig. 9a. — ,, ,, ,, side view. 
Fig. 10. — ,, Moma orion upper surface X 34 diam. 
Fig. loa. — „ ,, ,, side view. 
Fig. II. — ,, D. cceruleocephala upper surface X 26 diam. 
Fig. iia. — ,, ,, ,, ,, as naturally covered by maternal scales. 
Fig, iib. — ,, ,, side view. 
{To be continued^ 
MELANISM AND MELANOCHROISM IN BRITISH 
LEPIDOPTERA. 
By J. W. TUTT, F.E.S. 
{Continued from page 53.) 
1 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 
