On Aquatic Carnivorous Coleoptera or Dijtiscidce. 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 Laccophilini. [Vide]). 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 coxse 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 coxae 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- 

 cidse. A slight apparent approach is made to the Laccophiluii 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 



TBANS. HOT. DUB SOC, N.S., YOI.* II. Q Q 



