Notes in 1887 upon lepidopterous larve, dc. 597 
observed.) In shading the drawing of an object so as 
to represent roundness, the shade is made to become 
gradually less and less deep as the tangential planes 
represented come nearer and nearer to a right angle 
with the axis of vision. So here, the converse of shading, 
—the whiteness neutralising the shadow which shading 
is intended to represent,—dies off gradually as the 
midrib is approached. 
The whiteness is produced by the relative abundance 
of white dots and a fine white marbling of the surface 
which is present everywhere, mingled with the green. 
The effect is, in fact, produced by a process exactly 
analogous to stippling. 
By this beautiful and simple method a pupa, which is 
8°5 mm. from side to side in its thickest part, appears 
flat, and offers the most remarkable resemblance to a 
leaf which is a small fraction of 1 mm. in thickness. 
13. THE DEFENSIVE SECRETION OF THE LARVA OF CR&SUS 
varus.—The secretion of the ventral glands is distinctly 
acid to litmus paper. The smell caused by eversion of 
the glands after irritation, is said to be ‘‘ sour, like bruised 
sorrel-leaves.” It therefore seems clear that the de- 
fensive substance is a volatile acid, but the small size of 
the larve renders any further determination of its 
nature extremely difficult. 
14. THE GEOMETRIFORM STRUCTURE AND ATTITUDES OF 
Hucuip1a m1.—A very complete account of the Geometri- 
form structure of young Noctua larve, and of its bearing 
upon classification, was written by Professor Meldola 
(‘Trans. of the Epping Forest and County of Hssex 
Naturalists’ Field Club,’ June, 1881). The object of 
this note is to call attention to certain peculiar points 
in the Geometriform movements of the young larve of 
the genus Huclidia, and to introduce a figure of the 
young larva of H#. mi, in the 1st stage, in the Geometri- 
form attitude (Plate XVII. fig. 8, x 24:5). When I 
first saw the young larve of this latter species, I felt 
sure that they were Geometers, and yet I was struck by 
the extraordinary activity with which the larve whipped 
about the anterior part of the body several times 
between each stride, which was taken with extreme 
rapidity. I have never seen these movements con- 
