288 Mr. F. Walker's Characters of undescribed Diptera 



praebracliial vein rectangular, but with the angle somewhat 

 rounded ; discal transverse vein oblique, nearly straight. 



Length of the body I| lines; of the wings 3| lines. 



Mexico. 



Psilopus permodicus. 



Mas. — Aureo-viridis, gracillimus, antennis pedibusque' flave- 

 scente albis, alis limpidis, venis halteribusque pallidis. 



Male. — Golden-green, very slender : antennae and legs yel- 

 lowish-white ; wings limpid ; veins pale ; fore-branch of the prae- 

 bracliial vein obtusely rectangular; discal transverse vein oblique, 

 straight; hal teres very pale. 



Length of the body If line; of the wings 4 lines. 



Mexico. 



Fam. SYRPHID^. 



Genus Ceria, Fabr. 



Certa cacica. 



Fcem. — Nigra, nitens, capite antico pectoreque albido-tomen- 

 tosis, scutello albido, abdominis segmentis albido-maiginatis, 

 femoribus albido -strigatis, alis nigris postice cinereis, hal- 

 teribus albidis. 



Female. — Black, shining : head with a triangular patch of 

 shining whitish tomentum on each side in front ; antennae longer 

 than the breadth of the head ; first and second joints equal in 

 length ; third elongate-fusiform, much longer than the second ; 

 scutellum whitish; pectus with two whitish patches on each side; 

 abdomen with a whitish band on the hind border of the first, 

 second and third segments ; band of the third segment very 

 narrow ; femora with whitish streaks, those of the hind femora 

 very short ; wings black, greyish along the hind border ; halteres 

 whitish. 



Length of the body 8 lines ; of the wings 13 lines. 



Mexico. 



Genus Paragus, Meig. 



Paragns signatus. 



-Jineo-niger, capite albido, vitta antica fusc4 nitente, 

 antennis nigris, thoracis lateribus pectoreque testaceo-tomen- 

 tosis, abdomine testaceo vittis duabus lituraque nigris, pedi- 

 bus testaceis, femoribus tibiisque posticis nigro-fasciatis, alis 

 sub-cinereis fusco-sub-trifasciatis, halteribus testaceis. 



Female. — ^neous-black ; head with whitish tomentum ; front 



