On Aquatic Carnivorous Coleoptera or Dytiscide. G2 
Group 4. 
1140. Dytiscus tripunctatus, Ol., Trogus tripunctatus, M.C.—Ovalis, supra 
olivaceo-niger, capite anterius prothoraceque lateribus testaceis, elytris margine 
externo (cum epipleuris) argute et sat late testaceo ; subtus piceus, metathoracis 
episternis abdominisque lateribus testaceo-maculatis, pedibus quatuor anterioribus 
testaceis, femoribus anterioribus fusco-maculatis, tibiis intermediis fusco-testacels, 
tarsis intermediis pedibusque posterioribus piceis; antennis testaceis. Long. 
29231 m.m., lat. 11;—16 m.m. 
The anterior tarsi of the male are rather small; their pubescent area is of mode- 
rate size ; the intermediate tarsi have the two basal joints bearing well developed 
patches of moderately short sexual pubescence, and their claws are simple, very 
little unequal, and in fact scarcely different from those of the female. The female 
is either entirely without sexual sculpture, or may have on the basal portion of 
the wing-cases, very short irregular isolated scratches ; the thorax never shows the 
least trace of sexual sculpture. 
The species is very variable in size, form, and the sexual sculpture of the females, 
and shows even considerable variation in the sexual pubescence of the intermediate 
tarsi of the male, as well as in the width of the yellow marginal cincture which 
varies on head thorax and elytra. I have made a careful review of its numerous 
variations, and give below the results. It may be said roughly that there are four 
forms, an Eastern Asiatic one found in China, Japan, Formosa, Mantchuria, 
Philippine Islands, Malay peninsula, Hindostan, and Ceylon,—as well as in Austra- 
lia ; while the New Caledonia individuals approach the second form which is found 
in the islands of the Malay archipelago, from Sumatra to Celebes, the specimens from 
Bourbon and Mauritius approach very nearly to the Malasian specimens: the third 
form is rare and appears to occur in a sporadic manner in the Philippine Islands 
and the islands of the Malay archipelago. The fourth form is found in Africa 
and Southern Europe. 
The forms may be thus defined :— 
First, or east Asiatic form; moderate size, rather narrow and little convex form, 
sexual sculpture of the females either fine or entirely wanting ; and the patches of 
sexual pubescence on the intermediate tarsi of the male are rather narrow, that on 
the second joint especially being narrow, much narrower than that on the basal 
joint, 
The second or archipelagic form, is usually of rather broader, more robust and 
more convex form, the sexual sculpture of the females is very variable indeed, either 
entirely wanting or largely developed, and the patches of sexual pubescence on the 
male middle tarsi are broad, that on the second joint being scarcely larger than 
that on the first. 
The third or sporadic form is of large size, broader behind the middle than the 
