C «AP. IX. 
SPIDEKS. 
337 
acquired through sexual selection. Fritz Muller 12 gives 
Some striking instances of this law; thus the male 
s and-hopper (Orchestia) does not acquire his large 
claspers, which are very differently constructed from 
those of the female, until nearly full-grown; whilst 
young his claspers resemble those of the female. Thus, 
again, the male Brachyscelus possesses, like all other 
ainphipods, a pair of posterior antennas ; the female, 
and this is a most extraordinary circumstance, is desti- 
tute of them, and so is the male as long as he remains 
^nmature. 
Class, Arachnida (Spiders).— The males are often 
darker, hut sometimes lighter than the females, as may 
he seen in Mr. Blackwall’s magnificent work . 13 In 
some species the sexes differ conspicuously from each 
°ther in colour ; thus the female of Sparassus sma- 
Ta !/dulus is dullish-green ; whilst the adult male has 
the abdomen of a fine yellow, with three longitudinal 
Bi'ipes of rich red. In some species of Tliomisus the 
hvo sexes closely resemble each other ; in others they 
differ much; thus in T. citreus the legs and body of 
the female are pale-yellow or green, whilst the front 
legs of the male are reddish-brown: in T. floricolens, 
the legs of the female are pale-green, those of the 
^ale being riuged in a conspicuous manner with various 
tints. Numerous analogous cases could be given in the 
genera Epeira, Nephila, Pbilodromus, Theridion, Liny- 
pliia, &c. It is often difficult to say which of the two 
Se xes departs most from the ordinary coloration of the 
genus to which the species belong; but Mr. Elackwall 
12 ‘ Facts and Arguments,’ &c., p. 79. 
13 ‘ A History of the Spiders of Great Britain,’ 1861-G4. For the 
blowing facts, see p. 102, 77, 88. 
VOL. I. 
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