Ci ui>. yin. 
SEXUAL SELECTION. 
255 
cr ustaceans (e.g. Tanais) have imperfect, closed mouths, 
and cannot feed. The Complemental males of certain 
( 'h'i'ipedes live like epiphytic plants either on the female 
or hermaphrodite form, and are destitute of a mouth 
and prehensile limbs. In these cases it is the male 
’"'hick has been modified and has lost certain import- 
ant organs, which the females and other members of the 
®anie group possess. In other cases it is the female 
"’hick has lost such parts; for instance, the female glow- 
worm is destitute of wings, as are many female moths, 
s ome of which never leave their cocoons. Many female 
Parasitic crustaceans have lost their natatory legs. In 
s °me weevil-beetles (Cureulionidae) there is a great 
difference between the male and female in the length 
the rostrum or snout ; 2 but the meaning of this anti 
°f many analogous differences, is not at all understood, 
differences of structure between the two sexes in rela- 
tion to different habits of life are generally confined to 
the lower animals ; but with some few birds the beak 
°t the male differs from that of the female. No doubt 
‘ a most, but apparently not in all these cases, the dif- 
ferences are indirectly connected with the propagation 
°f the species : thus a female which has to nourish a 
Altitude of ova will require more food than the male, 
a fel consequently will require special means for procur- 
ing it. A male animal which lived for a very short 
time might, without detriment lose through disuse its 
0l ‘gans for procuring food ; hut he would retain his 
locomotive organs in a perfect state, so that he might 
rea ch the female. The female, on the other hand, 
foight safely lose her organs for flying, swimming, 
"’Sard to the statement about Tanais, mentioned below, I am indebted 
t0 Tritz Muller. 
2 Kirby and Spence, ‘Introduction to Entomology,’ vol. iii. 1S26, 
P. 309. 
