HYDROPHILIDZ. 53 
Fam. HYDROPHILIDZ. 
The family Hydrophilide consists of about 600 species, the majority of which are 
aquatic in their habits; nevertheless the family certainly cannot be correctly associated 
with the other aquatic families Haliplide, Dytiscide, and Gyrinide in the Adephagous 
series; it is indeed the first of a series of families of beetles that at present have not 
been satisfactorily combined in larger aggregates capable of exact definition ; some of 
these families comprise but a few species, and therefore exhibit but little variety of 
structural characters, while others are of greater extent and may be looked on as really 
equivalent in value to such families as the Carabide. ‘The Hydrophilide is inter- 
mediate in extent between these two extremes, but will probably become a family of 
even greater extent and importance than the Dytiscide; for the last-named family is 
rich in species in the waters of the more frigid portions of the earth’s surface, while 
this is not the case with the Hydrophilide, whose species appear to be more numerous 
in the warmer regions. The species of this family, except those of Europe and North 
America, have been and are much neglected by collectors and students ; and this is, in 
fact, the first time that any thing like a complete enumeration of the Hydrophilideous 
fauna of any considerable geographical region, other than the two just named, has been 
attempted. About 120 species have been already ascertained to be found in Mexico 
and Central America ; and although this number will no doubt be very largely increased, 
it is even at present about equal to the number of species of the family known to 
inhabit America north of Mexico. 
The classification of the family is in a very imperfect and unsettled stage, there being 
no conformity of opinion as to the number or limits of the tribes to be adopted in it, 
while the primary division of the family into two groups, Hydrophilini and Spheridiini, 
based on the comparative length of the joints of the hind feet, proves on examination to 
be quite untenable. Under these circumstances I have not thought it necessary for 
the purposes of this work to make use of any true classification, but simply to arrange 
the genera in conformity with the order in which they appear in the Munich Catalogue 
of Coleoptera; in this arrangement the species most profoundly modified for aquatic 
existence come first, and the terrestrial members of the family are placed at the end. 
Some authors make of the family Hydrophilide a series termed Palpicornia, supposed 
to be the equivalent of the Adephaga, while the minor divisions of the family are made 
to represent the families of the Adephagous series; this course, however, has nothing 
to recommend it, except an appearance of uniformity gained at the expense cf 
accuracy. 
