118 On some Best-attitudes of Butterflies. 



M. Oudeiuaus ouly treats of one aspect of the subject 

 which he deals with exhaustively by uumerous 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 

 foots 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 Chrysojjhanus ^jA/a'«s, L., sitting with 

 abdomen tilted up at an angle of about 45° to the thorax, 

 as I have shown in the specimen oi Eucldoe Iclcmia, 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 uumerous 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 

 10^ hours to a maximum of 13^ hours. 



But although the sun is visible for these long periods, 

 not so the butterflies. Ver\' 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- 

 light 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 ztvischen Fcirbrmg 

 iind Lehensgeicohnheit hci den Pcdaertischen Grossschmetterlingen 

 Yierteljahrsschrift der naturforsch. Gesellscliaft in Ziirich. XXXIX 

 Jahrgaug, 1894. (Read November 6, 1893.) 



t Mr. A. 1). Millar says that iu the afternoon female butterflies 

 are relatively more commonly seen. 



