62 
INTRODUCTION. 
sionally affording an olmous indication of the re- 
spectire 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 ( Hyfogrjwjrui ditpar J and 
several others. A few female moths are entirely 
apterous, or have wings of such a rudimentary kind 
as to be wholly imfit for flight, a pecidiarity which* 
may be witnessed in the well-knomi species named 
tlie Vapourer ( Orygia 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. Tlie case, indeed, is jirecisely analo- 
gous to that of the glow-wonn, whose “ nuptial 
lamp” has been long regarded, and to all appearance 
witli perfect propriety, os a‘ special prorfsion to meet 
this exigency. Even when both sexes arc ivingcd, 
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 casmd 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, partieul.arly 
