Vv ONISCOIDA—EPICARIDA 129 
The related Ligidiwm is found far inland, but always in the 
neighbourhood of water. These two genera may be distin- 
guished by the numerous joints in the flagellum of the second 
antennae, the flagellum being in all cases the portion of the 
antenna succeeding the long fifth joint. Philoscia muscorum 
occurs usually near the coast, but it is also found inland in 
England under trees in damp moss. This genus and the 
common Oniscus, found in woods, are distinguished by the 
presence of three joints in the flagellum of the second antenna. 
Philoscia can be distinguished from Oniscus by its narrower 
body and the pretty marbled appearance of its back. The 
genus Trichoniscus has four joints in the flagellum; various 
species are found in woods. In Porcellio and Armadillidiwm 
there are only two joints in the flagellum, while Armadillidium, 
the common garden wood-louse, can be distinguished from all 
others by the flattened shape of the uropods, and the habit of 
rolling up into a ball like an Armadillo. 
There is also a very peculiar species, Platyarthrus hoffmann- 
seggvt, Which occurs in England and Northern Europe, and 
always lives in ants’ nests. It is supposed that they serve as 
scavengers for the ants, which tend them carefully, and evidently 
treat them as domestic animals of some kind. The small creature 
is quite white and blind, and has exceedingly short antennae. 
Sub-Order 6. Epicarida. 
The Epicarida include an immense number of Isopods, parasitic 
upon other Crustacea. In the adult state they become greatly 
deformed, and offer very few characters of classificatory value, but 
they all pass through certain highly characteristic larval stages 
which are essentially similar in the different families. All the 
species are protandric hermaphrodites, each individual being male 
while in a larval state, and then losing its male organisation and 
becoming female as the parasitic habit is assumed. 
Two series of families are recognised according to the larval 
stages passed through, the Cryptoniscina, in which the adult 
male organisation is assumed in the Cryptoniscus stage, and the 
female condition is imposed directly upon this form, and the 
Bopyrina, in which the Cryptoniscus passes into a further 
larval stage, the Bopyrus, which performs the function of the 
VOLS Ly; K 
