118 On some Rest-attitudes of Butterflies. 
M. Oudemans only treats of one aspect of the subject 
which he deals with exhaustively by numerous observations 
on living specimens of all the chief groups of Macrolepi- 
doptera. His conclusions may be shortly expressed, almost 
in his own words, thus :—Lepidoptera have a sleeping- 
dress ; this dress forms a harmonious whole. The differ- 
ent parts which contribute to form the whole dress 
harmonize in their colours and usually in their patterns. 
The parts of the insect which are concealed during rest 
are quite frequently strongly contrasted in colour or 
pattern to the exposed parts. M. Oudemans explains the 
facts by the influence of exposure to light.* 
M. Oudemans does not allude to the points chiefly 
dealt with in this paper, but one of his beautiful pho- 
tographs shows Chrysophanus phleas, L., sitting with 
abdomen tilted up at an angle of about 45° to the thorax, 
as I have shown in the specimen of Luchloé belemia, Esp.., 
exhibited. He does not however call attention to its 
peculiar attitude. That it must greatly increase the 
resemblance to a dead leaf is obvious enough. 
In bringing this somewhat disconnected paper to a close 
I venture to make a remark which has a wide bearing on 
the whole question of cryptic and mimetic resemblances. 
Butterflies are most numerous and varied within the 
tropics. In the tropics the length of daylight varies much 
less than in temperate zones, and is many hours shorter 
than in the temperate summer. At the equator the sun is 
above the horizon for twelve hours every day; at the 
tropics the sun is above the horizon from a minimum of 
103 hours to a maximum of 134 hours. 
But although the sun is visible for these long periods, 
not so the butterflies. Very few comparatively are to be 
seen on the move before 9 a.m., and few after 3 p.m.t 
Now my point is that tropical birds, lizards, and other 
insectivorous animals have some six hours of full day- 
ligbt in which to hunt butterflies, when the latter are 
more or less at rest. This is a fact not usually allowed for 
in the discussion of questions of protective resemblances or 
mimicry, but it emphasises the need for concealment. 
* Compare Dr. M. Standfuss, Die Beziehungen zwischen Ferbung 
und Lebensgewohnheit bei den Palaertischen Grossschmetterlingen 
Vierteljahrsschrift der naturforsch. Gesellschaft in Ziirich, XXXIX 
Jahrgang, 1894. (Read November 6, 1893.) 
7 Mr. A. D. Millar says that in the afternoon female butterflies 
are relatively more commonly seen. 
