1332 COLEOPTERA 



while sometimes tlie scutellum is more or less flavescent. The 

 yellow colour of the undersnrface is sometimes somewhat embrowned 

 in parts, this being perhaps due to decomposition. The spine at 

 the outer angle of the hind femora is sometimes more prolonged and 

 distinct tlian in other cases. The sulcation of the prosternum is 

 peculiar, and seems to be formed by two very obsolete slightly- 

 raised lines, proceeding from each front angle of the middle portion, 

 and extending backwards about as far as the lower part of the 

 coxae. - 



Australia. Tasmania, and New Zealand. 



141. H. hookeri. {SJiarj) ; Aquatic Coleop., p. 104:.) Ovalis, 

 sat convexus, supra niger, capite anterius prothoraceque ad latera 

 testaceis, elytris vitta marginali, posterius angustissima, testacea ; 

 subtus nigro-piceus, pedibus anterioribus testaceis, femoribus in 

 medio piceis, pedibus intermediis piceo-testaceis ; femoribus posteri- 

 oribus angulo posteriori-exteruo acuto, parum producto ; prosterno 

 angusto obsoleteque sulcato. 



Long., 25mm. ; lat., 13mm. 



This species is closely allied to H. scutellaris, but is readily 

 distinguished by the colour of the undersnrface ; the groove of the 

 prosternum, though formed in a similar manner to that of H. 

 scutellaris, differs by the lines which bound it becoming more 

 approximate, and also by its being continued along the prosternal 

 process. The sexual characters in male and female are almost 

 identical with those of H. scutellaris. The few specimens I have 

 examined show very little variation. 



New Zealand. 



Rhantus. 



{Sharp; Aquatic Coleop., p. 899.) 



Side pieces of the fourth and following ventral segments very 

 narrow ; metasternal groove distinct and well defined, and the ter- 

 minal joint of the hind tarsus not longer (or but little longer) than 

 the preceding one. 



The forty species are distinguished constantly from their allies 

 by the above characters, as well as by two others which are not 

 quite so constant : these are, first, that the i^rothorax has a distinct 

 lateral margin ; and, second, that the swimming legs are rather well 

 developed, the femora having their undersnrface forming a developed 

 lamina towards the extremity. The coloration of the upper surface 

 usually is yellow, with black specks on the wing-cases, but in some 

 species it is entirely black, and in other cases nearly so ; where the 

 wing-cases are nearly but not entirely black it is generally the mar- 

 gins that are pale, and the black colour seems to have been produced 

 by a coalescence of the black specks. The prosternal process is 

 moderate in length, never elongate, nor very short, and neither 

 slender nor broad, always distinctly compressed. The metasternal 

 groove, though not elongate, is perfectly well developed, the middle 

 C0X8D never being so much approximated as to interfere with its 



