On Aquatic Carnivorous Coleoptera or Dytiscide. 199 
sively minute interstitial sculpture, having a somewhat granular appearance. 
Passing to the Dytiscini we meet in that group with some most remarkable facts : 
in the genus Hyderodes the females are usually smooth and polished like the males, 
but they are dimorphic, inasmuch as a second form of the female is met with 
(apparently only rarely) in which the surface is excessively rough, the whole of the 
upper surface, except the head, being covered with deep coarse erosions or corru- 
gations, irregular in shape and direction. In the genus Dytiscus considerable dis- 
erepancies exist among the various species in the sexual sculpture; in D. 
punctulatus the female has ten grooves on the basal portion of the wing-cases, and 
the whole of the rest of the upper surface, including the interstices of these grooves 
bears a close fine punctuation, while in the male the grooves are wanting, and the 
elytra are punctured only on the apical portions ; the female in this species has also 
even the undersurface rendered dull over a considerable portion of its area by the 
existence of fine, short scratches or reticulations which are not found in the 
other sex; in D. fasciventris the facts are similar except that the fine sculpture is 
less extensively developed, so that as regards this latter peculiarity the sexes are 
more alike than they are in D. punctulatus. In Dytiscus habilis, in D. hybridus, 
and in D. verticalis the females have no grooves on the wing-cases, but they difler 
from the males by a greater development of the punctuation on the apical portion 
of these parts, and also by possessing an additional fine punctuation on the lateral 
basal portion of the wing-case ; in D. verticalis this additional punctuation is very 
small and unimportant ; the females of these three species all possess too a con- 
spicuous special sculpture on each side of the prothorax ; in D. sublimbatus 
the female characters are approximately the same as in D. punctulatus and 
fasciventris, but in this species there also exist females differing in sculpture from 
the males only by their possessing a fine scanty punctuation on the lateral portions of 
the prothorax ; a similar condition is present in Dytiscus marginalis, the females 
differing greatly from the males by their grooved and much punctate surface, but 
individuals of their sex are found differing from the males only by a slight punc- 
tuation on the thorax and alittle greater development of that on the elytra. In 
D. circumcinctus we again find the females possessed of a grooved and much 
punctate surface, but here a second form of the female occurs quite without sexual 
punctuation or grooving of the wing-cases. ‘The females in the genus Dytiscus 
differ then from the males by possession of a fine sexual sculpture, and by a groov- 
ing of the elytra, this latter feature is however not found in certain species, and in 
certain other species is sometimes present, sometimes absent, while the fine sexual 
sculpture of the females is more constant, but may also be occasionally quite absent, 
and is only present in its greatest development in such females as are sulcate. In 
the Hydaticides, we find certain species of Acilius possessing females with grooved 
wing-cases, but the grooves are very different from what exists in Dytiscus, they 
being but four (instead of nine or ten) in number, and furnished with a pubescence 
