Thorax much' broader than long - - Lebia. 

 3. Fourth joint of anterior tarsi simple (fig. 1, anterior tarsus of Bromius 

 linearis.) 



a. Size over \ inch. 



Elytra blue-black - - Brachinus. 



Elytra brown or pitchy. Head contracted behind to form a distinct 



neck, elytra parallel sided - - Polystichus. 

 Head not contracted behind ; elytra rounded at sides - - Cymindis. 



b. Size under J inch. 



Elytra blue or green - - see Brachinus. 



Elytra pale yellow, brown, or black, or with dark markings ; antennas 



and legs yellow - - Bromius. 

 Antennas and legs black or dark brown - - Blechrus, Metabletus, 



and Lionychus. 



B. Anterior tibise furnished with strong spines - - Masoreus. 



BRACHINUS. 



The commonest British species, B. crepitans, can hardly be mistaken for 

 any other British beetle. The head and thorax are bright red whilst the 

 elytra are deep blue-black ; the antennas red, with the exception of the 2nd, 

 3rd, and 4th joints, which are more or less dusky ; and the legs are red. 

 The specific name has reference to its power of defending itself from its 

 enemies by producing a discharge of acrid vapour from the anus, attended 

 with a crackling sound — whence the name " Bombardier " beetle, which is 

 sometimes applied to it. In the northern counties it seems to be quite un- 

 known, but where it does occur, on the banks of tidal rivers, as at Gravesend 

 and in the Isle of Wight, it is generally very abundant. Two other species 

 of Brachinus, or rather one other species (sclqpeta), and a doubtful species 

 (explodens) occur in England but rarely. They are both much smaller (2-3 

 lines.) B. sclopeta, only a few specimens of which have been recorded, 

 and those principally from the south coast, is easily recognised by its having 

 a bright red dash at the base of the suture of the elytra ; while explodem is 

 said to differ from crepitans by its smaller size, and by having scarcely any 

 distinct strias on the elytra. 



DRYPTA. 



D. dentata, the only British species, is easily recognised from the descrip- 

 tion given above. It is a beetle which measures nearly half-an-inch in 

 length, but is a prize, only having occurred in a few localities in the south. 



POLYSTICHUS. 



The British species P, vlttatus is easily distinguished from all other Brit- 



