MTJTILLA. 291 



middle ; the raised part behind it has a perpendicular slope and is distinctly margined 



at the top, which is black. The first ventral segment is black at the base, where 



laterally there are some stout keels ; the keel is distinct and straight, and ends in a 



triangular tooth. The apex of the hypopygium is roundly incised ; towards the apex 



in the centre there is a triangular projection, ending in a blunt tooth. The legs are 



densely covered with pale hair ; the calcaria are white. The radial cellule is very 



broad, and extends beyond the third cubital cellule ; the basal abscissa of the radius is 



oblique and shorter than the apical, which is broadly elbowed in the middle. The 



second cubital cellule at the top is a little wider than the space bounded by the first 



recurrent and the second transverse cubital nervures ; at the top the third cubital 



cellule is about half the length of the bottom, and a little longer than the space bounded 



by the second recurrent and the third transverse cubital nervures. The first and 



second transverse cubital nervures are curved, the third sharply elbowed above the 



middle. The transverse median nervure is received in front of the basal nervure. 



This species may be known from most of the others with reddish abdomen by the 



basal abdominal segment not being black, the black teeth at its base stout, its apex 



distinctly and sharply depressed, and roundly incised in the middle. In having the 



base of the abdomen red and the apex of the pygidium excised it agrees with M. chroma 



( 6 ), but that species is smaller and more slenderly built. M. chroma also has the wings 



more lightly coloured; the first recurrent nervure received nearer the middle, so that 



the top of the second cubital cellule is equal to the space bounded by the first recurrent 



and the first transverse cubital nervures (the latter, too, being longer than the top in 



M. forreri) ; and the second recurrent nervure received in the middle of the cellule 



(in M. forreri beyond the middle). Structurally, they may be easily separated by the 



keel on the basal ventral segment in M. chroma abruptly projecting at the apex into 



a tooth ; while in M. forreri the keel gradually raises from the base to the apex, 



without projecting into an upraised tooth. 



/ 

 v 36. Mutilla Chroma. (Tab. XIII. fig. 22, <j organ.) 



Long. 10 millim. <$ . 



Hab. Mexico, Presidio de Mazatlan (Forrer). 



Head narrower than the thorax, densely covered all over with a thick dark silvery 

 pubescence, and on the vertex with long pale fuscous hair, the sculpture hidden by the 

 hair; the apex of the clypeus rounded; the mandibles piceous before the apex. 

 Behind the eyes the head is not much developed and not much narrowed. The scape 

 of the antennae covered with rather long silvery hair ; the flagellum with a dull pile, 

 its basal joints closely united, the third joint very slightly longer than the fourth. 

 The pronotum punctured ; its apex bluntly angulated in the middle, covered with a 

 broad belt of silvery pubescence, the rest with longish hair. The mesonotum rather 

 shining, coarsely, rugosely punctured, sparsely covered with blackish hair. The 



2pp2 



