TRIRHOGMA. 261 



to the base of the mandibles ; ocelli complete, round, rather 

 small, placed in a triangle on the vertex, somewhat close to- 

 gether; antennae filit'orm, inserted beneath 

 a rounded tubercle which is concave above ; 

 mandibles broader in the male than in the 

 female ; pronotum somewhat as in Doli- 

 cliurus^ with its posterior margin transverse 

 and the lateral angles tuberculate ; meso- 

 notum short, its posterior margin not 

 extending beyond the posterior margin oi: 

 the tegiilae ; median segment broad, flat 

 above, with broad prominent lateral pro- 

 pjg. ij-]^ jections, truncate posteriorly, the sides not 



Trirhogma cmrulca, $ , |. coming to a sharp angle and not tubercu- 

 late as in Am2iule.v, traversed dorsally and 

 on the sides above by several longitudinal carinae ; legs long, 

 slender, the intermediate coxae not very ^^adely separated, the 

 coxsB and trochanters of all the legs remarkably long, the femora 

 broad and flattened towards the base ; intermediate and posterior 

 tibiae and tarsi slightly spicose, intermediate tibiae with two apical 

 spines, anterior tarsi not ciliated, claws unidentate in the middle 

 below. Wings rather short ; fore wing with the radial cell 

 narrow, acute at apex ; three cubital cells ; the 1st equal or nearly 

 equal on the cubital nervure to the 2nd and 3rd united, receiving 

 the 1st recurrent nervure very close to or at its apex ; the 2nd the 

 smallest, the 1st and 2nd transverse cubital nervures enclosing it, 

 arched outwards, then strongly constricted towards the radial cell, 

 the 2nd recurrent nervure received at its apical third ; the 3rd 

 cubital cell broader at apex than at base. Abdomen broad, 

 depressed, often with only three visible segments; the apical 

 margins of the basal two strongly constricted. 



Nothing, so far as I know, is on record as to the habits of the 

 two species of Trirhogma found within our limits. 



J^ey to the Species. 



a. Abdomen smooth ; mandibles black T. ccerulea, p. 261. 



b. Abdomen delicately punctured; mandibles white 



at base T. prismatica, p. 262. 



483. Trirhogma caerulea, Westto. Trans. Ent. Soc iii, p. 225, pi. xii, 

 figs. 3 c? ) 3 a to 3 e ; Smith, Cat. iv, p. 273 ; Cain. Mem. Manch. 

 L. Fh. Soc. (4) ii, 1889, p. 114. 



5 . Head in front closely and finely punctured ; vertex, back of 

 the head, pro- and mesouotum, scutellum, and postscutellum with 

 a few scattered punctures ; abdomen smooth, brilliantly polished 

 and shining ; clypeus slightly convex, its anterior margin arched ; 

 pronotum rising posteriorly, with the margin behind transverse 

 and its lateral angles tuberculate ; median segment broad, with 

 four medial carinae arranged more or less in W-shape and two 

 outer lateral carinae, the space between the carinse reticulate. 



