On Aquatic Carnivorous Coleoptera or Dytiscide. 923 
No 630) much approximates the Vatellini in form, and has also the mesosternum 
more than usually exposed, and even makes some approach to the Vatellini by a 
greater than usual elongation of the front tarsi. 
The external sexual differences in the Vatellini are apparently confined to the 
front and middle tarsi. 
The group as at present known is peculiar to the warm parts of South America, 
but I shall not be at all surprised if it be found to have representatives in Patagonia. 
II. 5.—Group Laccoputunt. (Vide p. 286.) 
This aggregate of the second degree consists only of two most unequal genera, 
one being an autogenus, the other comprising eighty-three species. 
It is not necessary to repeat all that has been said of the structure of Laccophilus. 
The Laccophilini are insects of small size, of very continuous outline, and with very 
little sculpture of the surface. The prosternum in front of the coxze continues the 
plane of the prosternal process, which is always very acuminate at its apex ; the 
metasternum is very elongate in the middle and very reduced at the sides by the 
encroachment of the hind coxee so that it forms on each side a slender curved band. 
The sides of the prothorax are without lateral margin, and the scutellum can never 
be perceived, the base of the thorax being either straight in the middle (Nepto- 
sternus) or more or less acuminate (Laccophilus). The front and middle tarsi are 
five-jointed, the fourth joint being similar to the third in form and size; in the 
male they are but little dilated. The swimming legs are moderately or highly 
developed, and their tarsi have a lobing of the joints which is very conspicuous in 
Laccophilus, less so in Neptosternus. 
The Laccophilini are a very distinct group, and there is no real connection 
between them and any other group. The Noterini agree with them in having a 
concealed scutellum and the five-jointed tarsi, but are extremely different by the 
structure of the mesosternum, and other points; and in fact in many important 
respects the two groups are amongst the most absolutely different of all the Dytis- 
cide. A slight apparent approach is made to the Laccophilini by Coptotomus of 
the Colymbetides, and if a Coptotomus, say Dytiscus interrogatus, Fab., be compared 
with a Laccophilus much resembling it, viz., C. quadrilineatus, Horn, the two will 
appear to have so great a similarity in form, colour, markings and some important 
particulars of the structure that a real approximation might easily be considered 
established; but in other and more important respects, such as the very different 
coxal lines and processes, and the scutellum, the two forms are profoundly divergent; 
and it is clear that the resemblances are due to the common life of the two. There 
is not the least reason to believe that the similarities are to be ascribed to any 
descent from a common ancestor, but it is quite satisfactory to believe that they 
TRANS. ROY. DUB SOC., N.S.,, VOL. U, 6c 
