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The Descent of Man

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mals, we can understand why she has been<br />

rendered so much more luminous and conspicuous<br />

than the male; and why the larvae themselves<br />

are likewise luminous.<br />

DIFFERENCE IN SIZE BETWEEN THE<br />

SEXES.<br />

With insects <strong>of</strong> all kinds the males are commonly<br />

smaller than the females; and this difference<br />

can <strong>of</strong>ten be detected even in the larval state. So<br />

considerable is the difference between the male<br />

and female cocoons <strong>of</strong> the silk-moth (Bombyx<br />

mori), that in France they are separated by a<br />

particular mode <strong>of</strong> weighing. (13. Robinet, 'Vers<br />

a Soie,' 1848, p. 207.) In the lower classes <strong>of</strong> the<br />

animal kingdom, the greater size <strong>of</strong> the females<br />

seems generally to depend on their developing<br />

an enormous number <strong>of</strong> ova; and this may to a<br />

certain extent hold good with insects. But Dr.<br />

Wallace has suggested a much more probable<br />

explanation. He finds, after carefully attending

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