620 On Aquatic Carnivorous Coleoptera or Dytiscide. 
middle tarsi are clothed beneath in a similar manner to the front feet, and their 
claws are moderately long, the outer being a good deal thicker and longer 
than the inner one. The females have a slight difference of sculpture from the 
males, the reticulations of the elytra on the basal portion becoming a little coarser 
in a stripe-like manner ; this sculpture is very distinct in the specimens from. North 
America and Lapland, but in individuals from Central Europe can often be scarcely 
detected. 
Europe, Siberia, and North America. (Sweden; Lapland; Finland to 68° 30’ Sahlberg; Britain ; 
Belgium ; Northern France ; Germany ; Hudson’s Bay ; Massachusetts). 896. 
950. Colymbetes tostus, Lec., M.C.—Ovalis, elongatus, minus convexus, testaceus, 
vertice late nigro, elytris nigro-irroratis ; tarsis posterioribus articulo quarto extus 
vix lobato-producto. Long. 103, lat 54 m.m. 
The male has the front tarsi much incrassate, and comparatively little compressed, 
and furnished beneath with large palettes, the marginal hairs are largely developed 
and have beautifully curved extremities; the claws are elongate and slender, the 
hinder being a little shorter than the front one; the middle tarsi are clothed 
beneath in a similar manner to the front feet, their claws are rather long and not 
thickened, the inner distinctly shorter than the outer one. 
North America, (Missouri). 897. 
951. Dytiscus exoletus, Forst., Rhantus exoletus, M.C_—Ovalis, parum convexus, 
testaceus, vertice nigro-variegato, elytris nigro-irroratis ; tarsis posterioribus articulo 
quarto extus lobato-producto. Long. 10, lat. 52 m.m. 
The male has the frout tarsi moderately incrassate and a good deal compressed, 
and furnished beneath with moderately large palettes, the marginal hairs are not 
highly developed, the claws are very long and slender, the hinder one a little 
shorter than the other; the middle tarsi are clothed beneath in a similar manner to 
the front feet, and their claws are rather long and slender, the inner one being a 
good deal shorter than the outer. There is no sexual difference in the sculpture of 
the elytra; the apical ventral segment is in each sex indistinctly strigose in the 
longitudinal direction. 
Although the thorax in this species is generally immaculate, it has sometimes a 
round dark spot on each side of the middle near the base, and these spots are con- 
nected together: by a fuscous basal mark. Dytiscus melanopterus, Zett. (Faun. 
Lapp. I, p. 211) is considered to be a colour variety of this species. 
Europe, (Sweden, Finland, Lapland, Britain, France, Belgium, Germany, Algeria), 898. 
