6i 4 M. W. R. de V. GRAHAM 



relatively shiny, its hind margin deeply emarginate ; plicae absent, or 

 indicated only posteriorly ......... 20 



- Gaster short ovate to lanceolate (1-4 to 3-6 times as long as broad), from 



about as long as the thorax to slightly longer than head plus thorax ; but 

 even in examples having the longest gasters, the last tergite is at most 

 1 *5 times as long as its basal breadth. Except in Ch. diver sus Walker, 

 the propodeum (Text-figs. 491, 493) is about half as long as the scutellum, 

 with its median area distinctly produced behind the level of the supracoxal 

 flanges (which are strongly curved) and more strongly sculptured, its hind 

 margin shallowly emarginate ; the plicae are usually distinct. 



Ch. diversus, in which the propodeum is like that described in the alternate 

 part of the couplet, has the gaster at most 3-2 times as long as broad, and 

 the last tergite hardly longer than its basal breadth ..... 5 



5 (4) Mid leg with tibial spur half, or even slightly more than half, as long as the 



maximum length of the first tarsal segment ; legs relatively short and 

 stout. In most species the antennal clava (Text-figs. 497-500) is short, in 

 profile asymmetrical, the dorsal edge being more strongly curved than the 

 ventral edge, with the dorsal surface of its second and third segment more 

 densely hairy than the rest. Costal cell of fore wing without hairs upon its 

 upper surface. Gaster often less than twice as long as broad. . . 6 



- Mid leg (Text-fig. 490) with tibial spur obviously less than half the maximum 



length of the first tarsal segment ; legs long and slender. Antennal clava 

 (Text-figs. 504, 506) appearing symmetrical in profile with the dorsal sur- 

 faces of its second and third segments not more densely hairy than the rest, 

 except in Ch. pilosus, in which the fore wing (Text-fig. 508) has a few hairs 

 upon the upper surface of the costal cell near its apex. Gaster 2-3 to 3-6 

 times as long as broad ......... 19 



6 (5) Antennal clava (Text-figs. 497-500) in profile appearing asymmetrical, the 



dorsal surface of its second and third segments clothed with a dense pile of 

 hairs ; the clava itself short, not or hardly twice as long as broad, the lines 

 separating its segments tending to be oblique. Combined length of pedi- 

 cellus and flagellum usually equal to or less than the breadth of the head, 

 rarely very slightly greater. Pronotal collar as a rule less distinctly margined, 

 the margin often irregular, or sharp only medially .... 7 



- Antenna (Text-fig. 506) ; clava in profile appearing symmetrical, the dorsal 



surface of its second and third segments without dense pilosity ; com- 

 bined length of pedicellus and flagellum usually slightly greater than, at all 

 events not less than, the breadth of the head. Pronotal collar, except just 

 at the sides, with a fine but sharp margin . . . . . . 13 



7 (6) Gaster (Text-fig. 486) ovate-lanceolate to lanceolate, two to three times as long 



as broad, nearly or quite as long as head plus thorax, or even longer in some 

 specimens of phalaridis, especially those under 2-5 mm. in length ; last 

 tergite usually as long as, or longer than, its basal breadth ; distance from 

 base of eighth tergite to tip of gaster usually obviously greater than the 

 length of the basal tergite ......... 8 



Gaster (Text-figs. 487, 488) ovate, less than twice as long as broad and not 

 longer than the thorax ; last tergite shorter than its basal breadth ; 

 distance from base of eighth tergite to tip of gaster less than the length of 

 the basal tergite ........... 9 



8 (7) Tip of hypopygium situated at about one third, or slightly less, the length of 



the gaster. Antenna (Text-fig. 498) with proximal funicular segments 

 relatively elongate, the fourth distinctly longer than broad ; length of 



