104 Mr. D. Sharp's revision of the species 



distinguish the sexes. The epipleural margin is con- 

 spicuously punctured up to the base, and the ventral 

 spine is elongate and rather slender. 



Group 5. Sternal spine broad and rather flat and short, 

 but extending beyond the first ventral suture ; pubescent 

 area of posterior femur of large extent, occupying about 

 one-half of the lower face of the femur ; last ventral 

 segment armed ivith elongate spine ; stature large. 

 (Species 15 to 17). 



15. Hydropliilus apicipalpis, Chev. 



Chew, Col. Mex., fasc. 3. 



Mexico ; Guatemala ; Colombia ; Cayenne. 



This species is of large stature, and usually black in 

 colour, with a slight aeneous tinge, but occasionally the 

 surface shows somewhat brilliant metallic reflections ; 

 the punctuation of the wing-cases is very dense and even, 

 and, although very fine, is quite distinct, and there may 

 always be detected (when a specimen is well cleaned) on 

 each wing-case the rudiments of seven or eight striae 

 formed by lines of very fine punctures. The form is 

 peculiar, the hind portion of the wing-cases is more 

 elongate than usual, and so the posterior part of the body 

 appears more acuminate. The male has a very fine 

 tooth at the base of the under claw on the middle and 

 hind feet. 



16. Tropistemus chalybeus, Cast. 



Cast., Hist. Nat. ii., p. 53. 



T. nitidus, Cast., I. c. 



Hydropliilus chalybeatus, Curt., Trans. Linn. Soc. xix., 

 p. 42. 



Mexico; Guatemala; Panama; Colombia; Cayenne; 

 Amazons (from water standing in a canoe, Rio Sappo, 

 21st Nov., 1874, Prof. Trail) ; Brazil ; Guadeloupe. 



This species is readily distinguished by the beautiful 

 colour of the upper surface, which is violet, purple, or 

 blue. It varies a good deal in size and in the colour of 

 the legs, but I am unable at present to distinguish more 

 than one species. I have preferred the trivial name of 

 chalybeus to that of nitidus, although the two were pub- 

 lished at the same time, because there exists also a 

 nitidulus and a nitens in the genus. 



