On Aquatic Carnivorous Coleoptera or Dytiscide. 583 
has the meshes of the reticulation on the elytra comparatively broader and shorter, 
and the prosternal precess less compressed at the sides. 
Europe, throughout, from Iceland and 69° North according to Sahlberg, to Spain and Portugal ; Corsica ; 
Sardinia, Sicily, Algeria, Syria, Persia. 805. 
The variation found in this species is very complex and interesting. The ordinary 
form may be considered to be that in which the female has the surface duller than 
the male and the longitudinal scratches finer, denser and more oblique, the general 
form in both sexes being rather regularly oval, the female however being generally 
just a little narrower and more oblong than the male: on examination under the 
compound microscope with a half-inch object glass, it appears that the dullness of 
the surface in the female is caused by minute scale-like reticulations, which are 
not so deep in the male as in the other sex : this form is that universally found in 
temperate Kurope, and I have it in my collection from as far east as Persia: the 
size about J—11 m.m. long, 5—5z m.m. broad: this may be called the ordinary 
or typical form. in some of the warmer parts of Europe, there are found large 
specimens in which the sculpture in the female is quite similar to that of the male, 
which, as in the ordinary form just mentioned, consists of very elongate, narrow 
meshes on the basal portion of the elytra: this may be called the South European 
variety. In the highland districts of Britain, and in the Alps and Iceland, the 
specimens become smaller, and of a narrower, more oblong and depressed form 
with the base of the thorax narrower than that of the elytra, andthe surface in 
the female excessively duil, so that the disparity in the appearance of the two sexes 
is very great : but this fori (for females of which Aube proposed the name “ Agabus 
solieri”) is connected with the common temperate European form by everv shade of 
intermediate variation: this may be called the dimorphic Alpine form. In some 
localities in the Alps and Pyrenees there are found (I believe always ata great 
elevation) specimens of elongate, narrow and depressed form, with very shining 
surface, tne sculpture in the female being similar to that of the male, and the meshes 
of the reticulation of the elytra are generally rather broader and shorter than in 
the ordinary temperate European form. This form has been found by Kiesenwetter 
in the Alps of Carniola; and has also occurred at Lago Pinter, and in the Hautes 
Pyrenees; it may be called the monomorphic Alpine form. We have thus the 
peculiar anomaly that in some Alpine districts the sexual divergence in sculpture 
of the female from the male is much increased, while in other Alpine districts there 
is on the contrary convergence of the sculpture of the female to the male, or in fact 
absolute similarity. I have no evidence that these two Alpine forms of the female 
are ever found together, indeed all the evidence I have indicates the contrary ; thus 
though I have found great numbers of the dimorphic Alpine form in the mountains 
about Braemar, I have never found a single female with sculpture at all like that 
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