62 INTRODUCTION. 



sionally affording an obvious indication of the re- 

 spective sexes. In several cases the colours and the 

 mode of their distribution are so dissimilar, that 

 when taken in connexion with other strongly marked 

 differences, they would lead an observer, ignorant of 

 the relations that subsist between them as proved 

 by other circumstances, to refer the two sexes to 

 entirely different genera. An example of this is 

 seen in the Gipsey-moth (Hypogymna, dispar) and 

 several others. A few female moths are entirely 

 apterous, or have wings of such a rudimentary kind 

 as to be wholly unfit for flight, a peculiarity which 

 may be witnessed in the well-known species named 

 the Yapourer (Qrygia antiqua). 



In such instances as that just mentioned, it is 

 evident that the sexes would often experience the 

 utmost difficulty in discovering each other, unless 

 they were possessed of some peculiar means for 

 that purpose. The case, indeed, is precisely analo- 

 gous to that of the glow-worm, whose " nuptial 

 lamp " has been long regarded, and to all appearance 

 with perfect propriety, as a special provision to meet 

 this exigency. Even when both sexes are winged, 

 as is usually the case, a speedy introduction to 

 each other's society is too necessary a step to be left 

 to the chances of a casual encounter, as many of 

 them are extremely short-lived, and not very loco- 

 motive in their habits ; and an opportunity might 

 thus be wanting to execute a function for which 

 alone, in many cases, they seem to enter upon their 

 winged state. The males, accordingly, particularly 



