62 



INTRODUCTION. 



Family G. DYTISClDiE. 



Antenna; inserted dose to the eye and close to the upper portion 

 of the base of the mandibles, eleven-jointed, glabrous and shining, 

 and entirely destitute o f seta; or pubescence ; head short and broad, 

 sunk in the prothorax as far as the eyes, clypeus not extending 

 laterally beyond the insertion of the antennas ; metasternum ivithout 

 any cross suture, produced behind into an angular process ; hind cocoas 

 very large, soldered with and appearing as part of the metasternum, 

 reaching the margin of the elytra ; posterior legs modified for 

 swimming, tibia} and tarsi furnished with swimming hairs, as a 

 rule broadened and f attened ; abdomen with six visible ventral 

 segments. 



The great authority on this group is Dr. Sharp, and his exhaustive 

 work " On Aquatic Carnivorous Coleoptera or Dytiscid^u," 

 published in the Transactions of the Koyal Dublin Society (vol. ii, 

 series 2, 1880-2), is by far the most important that has yet 



Fig.*27. — Bytiscus (Troy its) limbatus and the under surface of the front 

 tarsus (enlarged). 



appeared. He divides the Dytiscid.e into two great series, the 

 Dytisci fragmentati in which the metathoracic episternum does 

 not reach the middle coxal cavity, and the Dytisci complicati in 

 which the metathoracic episternum reaches that cavity. 



Excluding the Hygrobiidje or Pelobiid^: and the AMPHizoiDiE, 

 which Dr. Sharp now considers to be separate families, we have 

 the following table, drawn up by him ; the divisions, however, as 

 will be seen, are of very different values. 



