196 SHARP: HYDRADEPHAGA OF LANCASHIRE AND CHESHIRE, 
2.—Shortening of anterior legs, and rp eg (possibly for 
sexual purposes) of anterior tarsi in males 
3.—Lengthening of posterior legs, and sansa of vertical play 
o a lateral oar-like movement ; lateral compression of both 
posterior and, to some extent, median legs, and formation 
of thick fringe of hair to assist in propulsion. 
4-—Gradual alteration in contour, both horizontally and laterally ; 
smooth surface without striation in males, and recession of 
eyes into head. 
5-—Amplification and general use of wings. 
These, then, are the points which arrest our attention in our 
survey of the Hydradephaga from Ha/iplus to Dytiscus, but it must 
be noticed that we have not included that singular family of the 
Gyrinid@ in these remarks at all. In them we discover a far more 
extreme differentiation than these points we have recapitulated 
cover. The contour, indeed, remains much the same, but no 
further progression was easily possible beyond Agaéus and Dytiscus 5 
their lines are so fine as to be unsusceptible of improvement, but the 
foliowing features are distinctly unique : — 
1.—Eyes duplex, that is half the eye above, and half below 
the median line of the head so as to appear like four eyes 
instead of two. This arrangement is to subserve the needs 
of a life mostly passed on the surface of the water instead 
of in the depths. 
2.—Antennz shortened and compressed to a mere knob. 
3-—Anterior legs lengthened, but tarsal joints not enlarged. 
4.—Median and posterior legs shortened and extremely flattened, 
and tarsal joints flattened to the likeness of paddles and 
inserted differently from the usual plan. 
Such differences as these, so important and fundamental, have 
suggested the idea that this family of Gyrinide should be elevated 
to the rank of a sub-order, being as diverse from either Adephaga 
or Clavicornia as these groups are from each other, but as they are 
and always have been treated as part of Hydradephaga, we shall 
paren them iphone A in our consideration of that division. 
ally, we may remark that the Adephagous water-beetles afford 
pinctiend illustrations of the protective resemblance attained by 
is is seen in none of them better than in Zaccophilus 
hyalinus. ‘The colour of this beetle is a kind of dirty olive-gree? 
with a glassy semi-transparent look about it, than which no better 
tint could be imagined to conceal the creature in the still clear water 
of ponds full of semi-lights and reflections from water-plants. __There 
Naturalist, 
