| DESCRIPTION |
 |
Hydrophilids are largely aquatic in both the adult and larval stages. They
feed on algae and detritus in the adult stage and are predatory in the larval
stage. Some forms have evolved to live in very liquid dung or moist soil.
In the field they may be distinguished from dytiscids by their manner of
swimming: hydrophilids move their legs alternately (more of a crawling motion)
while dytiscids move their hindlegs synchronously.
The hind legs are flattened and fringed with hairs, modified for swimming.
They are similar to the
Dytiscidae
but have short, clubbed antennae that are often concealed. The maxillary
palps are elongate and frequently exceed the antennae in length. The enlarged
palps can be mistaken for antennae and because of this, confusion with
Dytiscidae
may be compounded. Thus it is important to be able to recognize both the
maxillary palps and the antennae on the hydrophilids. Frequently the metasternum
will bear a sharp spine. Other characters useful in separating these two
families are listed under
Dytiscidae.
Maxillary palps elongate, frequently long enough to be confused for antennae;
antennae clubbed and often concealed.