On Aquatic Carnivorous Coleoptera or Dytiscide. 699 
I. 75.—Genus HRETES. 
Thorax with a fine lateral margin. External margin of elytra armed with short 
spines, at some distance before the apex. 
Two species are known, one Australian, the other almost cosmopolitan. 
1095. Dytiscus sticticus, Linn., Hunectes sticticus, M.C\—Pallide testaceus, 
nitidus, vertice nigro-signato, elytris punctis magnis nigris impressis ; elytrorum 
humeris rotundatis, apice ad suturam acuminato, epipleuris angustissimis ; prosterni 
processu acuto. Long. 14, lat. 73 mm. 
Fem., elytris in latera ad medium depressione plus minusve elongata. 
Variat, statura plus minusve elongata, thorace in medio elytrisque pone medium 
plus minusve distincte nigro-fasciatis, his seepius ad latera in medio macula angus- 
tula nigra. 
The male differs from the female not only by the dilated anterior tarsi and 
absence of the lateral impressions on the wing-cases, but also a little in the form of 
the thorax, which appears less narrowed in front than in the female, and has its 
sides a little more, and its hind angles a little less rounded. 
The species besides varying much in size, shows a considerable variation in the 
black marks of the upper surface ; although these variations are not important, 
they have, in conjunction with the wide distribution of the species, led to the 
establishment of a considerable number of false species, for which after a very care- 
ful examination I find not the least justification. The species is in all its structural 
characters singularly constant, and with the following one, may be readily distin- 
guished from all others, by the peculiar serration of the edges *of the wing-cases, 
behind the middle ; this can only be seen with a good lens, and arises from the 
existence there of a considerable number of extremely short, thick and pointed 
setee or spines, ‘The hind tarsi are also very peculiar in this insect, inasmuch as 
they are punctate externally instead of being polished. Varieties have been 
described frequently as distinct species. If I am correct in supposing that E. 
punctipennis, Macleay, is this species, then Australia must be added to the localities 
mentioned below. 
Widely distributed in the warm portions of the Old World, apparently rare in 
America. It is worthy of note that this species is found in a greater number of 
islands than any other of the Dytiscide. 
France, Corsica, Sardinia, Spain, Africa ; Siberia, Japan, Formosa, China, Philippines, Timor, Sumatra, 
Java, Pulo Penang, Siam, India, Arabia, Mesopotamia; Canary Islands, Madeira, Cape Verde Islands ; 
United States of North America, Mexico, Peru; Guadeloupe, Galapagos. 954. 
TRANS. ROY. DUB. S0C., N.S., VOL. I. 4X 
