728 On Aquatic Carnivorous Coleoptern or Dytiscidce. 



other, the female sexual sculpture is very lai'gely developed, while the patches of 

 sexual pubescence on the intermediate tarsi of the male are largely developul as in 

 the second form. 



The fourth or African form is usually large and very elongate, with the yellow 

 cincture largely developed: the females never have the least trace of sexual sculp- 

 ture, and the patches of sexual pubescence on the intermediate tarsi of the male 

 are moderately developed, intermediate in size between those of the first and 

 second forms, but with the hairs usually rather longer than in either. 



The characters are however variable, and no definite limits can be assigned to 

 the four forms as will be seen from the following more detailed sketch of the local 

 variations. 



Japan. — Eight individuals from three sources are before me from this locality : 

 the smallest individual (a male) is 24 m.m. long, 12i m.m. broad, 7h m.m. high ; 

 the largest (a female) 28 m.m. long, 1 4| broad, Si m.m. high : the yellow mark on the 

 clypeus is broad, but shows in the middle a slight descent forward of the dark 

 colour : the thoracic and elytral bands are never very broad, but are distinctly 

 broader in some individuals than they are in others, the anterior tarsi of the male 

 attain fully la m.m. in the transverse direction; the pubescence on the basal joint 

 of the intermediate tarsi is intermediate in shape between a narrow triangle and 

 an oval form, and that on the second joint forms a patch which has a nmch less 

 width than the termination of the patch on the basal joint : the females have no 

 sexual sculpture. 



A female from Formosa agrees with the Japanese individuals ; while another 

 from Mantchuria differs only by having a fine but distinct sexual sculpture extend- 

 ing along the middle of the wing-case, from near the base to about one-third of the 

 distance towards the apex. 



Numei'ous specimens from China agree with the Japanese form, but some of the 

 females have a well marked sexual sculpture, while others have no trace of it ; the 

 largest individual is a female with well marked sexual sculpture, and agreeing 

 nearly in size with the largest Japanese female, being fully 28 m.m. long, 15 m.m. 

 broad, 9 m.m. high. In a large male the front tarsi attain quite 1| m.m. in the 

 transverse direction. 



Specimens from the Malay peninsula show no further vai'iation than those men- 

 tioned above ; the females have no sexual sculpture ; one male is of very diminutive 

 size, 22 m.m. long, Hi m.m. broad, 7 m.m. high. 



From the Philippine islands numerous specimens, (some of which are labelled 

 "Manilla") show no differences from the forms already alluded to : and the females 

 have also variable sexual sculpture, which is sometimes completely absent. Three 

 individuals from these islands differ, however, by their large size and by their form 

 which is more dilated behind ; the male has the patches of pubescence on the middle 

 tarsi much broadei", and the females a sexual sculpture on the elytra, consisting of 



