310 NORTH AMERICAN MUTILLIDAE 



7. Petiole not nodose, much widened toward the apex and sessile with the 



second segment, which is but little wider than the apex of the petiole; 

 second ventral segment never carinate. 



Pseudomethoca Ashmead, subgenus Xomiaephagus Ashmead 



Petiole only slightly enlarged at apex, constricted before the base of the 



second segment and often strongly nodose, the second segment much 



wider than the apex of the petiole. If the latter is sessile, the second 



ventral segment is carinate (8) 



8. Second ventral segment with a longitudinal keel surmounted by a crest of 



bristles Dasymutilla Ashmead, subgenus Bruesia Ashmead 



Second ventral segment without a keel, but often with a pit filled with 

 bristles Dasymutilla Ashmead, subgenus Dasymutilla Ashmead 



Females 



1. Petiole evenly and greatly enlarged toward the apex,^ not at all constricted 



but perfectly sessile with the second segment, which is not or but little 

 wider than its apex; front usually with a carina between the eyes and 



the bases of the antennae (2) 



Petiole constricted at its apex, which is not greatly, sometimes not at all 

 larger than the base; the second segment greatly wider than the first; 

 face rarely with a carina between the eyes and the bases of the antennae; 

 if so the postero-lateral angles of the head are carinate, or the insects are 

 large, densely yellow or scarlet and black tomentose (5) 



2. Inferior angles of the temples with a sharp spine; postero-lateral angles of 



head carinate; head very large, decidedly wider than the thorax; antennae 

 remote from one another at base; pygidium not defined. 



Pseudomethoca Ashmead, subgenus Pseudomethoca Ashmead 

 Temples without a spine, sometimes with a posterior carina; postero- 

 lateral angles of head unarmed (3) 



3. Eyes small and round, their width over .85 of their length (4) 



Eyes elongate, triangularly oval, their width und^r .7 of their length; the 



margin of the clypeus with a strongl}'^ arched median elevation, mar- 

 gined anteriorly and with median and two lateral teeth; front with a 

 carina between the antennae and the eyes; mandibles without a third 

 tooth within Mutilla Linnaeus, subgenus Timulla Ashmead 



4. Front with a carina between the eyes and the antennae; the clypeus with a 



transverse depressed basin above its margin, or its surface flat and smooth; 

 mandibles with a third tooth within. 



Pseudomethoca Ashmead, subgenus rfomiacphagus Ashmead 

 Front devoid of carinae; mandibles without a third tooth within. 



Photopsis Blake 



5. A distinctly defined pygidial area present, either striate, granulate, or 



rugose •. (7) 



No definite pygidial area present (6) 



2 This character does not apply to certain species of Pholopsis from the 

 western United States. 



