422 
of the under wing 0.65; the sum of the areas 
of the two wings consequently is =1.25; but 
when placed in the position of flight, as the 
anterior wing lies partially over the under wing, 
the whole effective surface of the two wings 
measures 0.83, and that of the four 1.66 in. 
During re the dorsal planes of the wings 
of the diurnal Lepidoptera are directed verti- 
cally and brought into contact. 
octurnal Lepidoptera,—Many of this order 
have large organs of flight; their wings, which 
in repose lie in or beneath the horizontal plane, 
are triangular, their apices being the most dis- 
tant points from the body when the wings are 
Fig. 
0.208 
MOTION, 
extended, and their areas are in the inverse ratio 
of their velocities, and their distances from he 
centre of gravity. Thus in the Erebus Strix Sig. 
221) the wings are greatly expandedand of a form — 
the best calculated for rapid flight, the i 
of the sections of the wing being, for the r 
part, in the inverse ratio of their distances fr 
the axis of motion; ne the re 
of that of the Pontia, the Morpho, and 
of the diurnal Lepidoptera. The anterior 
is much larger than the posterior, being 
7.175 to 5.095 square inches. The area | 
four wings is therefore about 12.270 inches, 
which, being very considerable in f d 
221. 
0.419 
0.707 
0.8314 
0.987 
1 
1.3225 
Areas within the parallels. 
1.5834 
1,5534 
oh 
1.545 
1.2 
