The pupae of caddis-flies inhabiting
streams have fringes of hair on the tarsi to enable them to reach the
surface on leaving their cases. But in the species inhabiting bromelia
leaves there is no need for swimming, and accordingly we find the tarsi
entirely bare. In the same plants are found curious little Entomostraca,
very abundant there but found nowhere else. These form a new genus, but
are most nearly allied to Cythere, a marine type. It is believed that
the transmission of this species from one tree to another must be
effected by the young crustacea, which are very minute, clinging to
beetles, many of which, both terrestrial and aquatic, also inhabit the
bromelia leaves; and as some water-beetles are known to frequent the
sea, it is perhaps by these means that the first emigrants established
themselves in this strange new abode. Bromeliae are often very abundant
on trees growing on the water's edge, and this would facilitate the
transition from a marine to an arboreal habitat. Fritz Mueller has also
found, among the bromelia leaves, a small frog bearing its eggs on its
back, and having some other peculiarities of structure.
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