278 CHARLES A. BLAKE. 



Myrmosa rufiventris Blake. 



Male. — Head large, black, quadrate, wider than the thorax, finely punctured, 

 thinly clothed with erect black hairs ; eyes ovate, prominent ; antennae black, 

 flagellum pruinose ; mandibles stout, thinly clothed with pale hairs ; thorax 

 ovate, narrowed posteriorly, mesothorax with two dorsal, longitudinal impres- 

 sions, scutellum convex, metathorax roundly truncate, closely and minutely 

 punctured ; wings hyaline, iridescent, marginal cell large, lanceolate, first sub- 

 marginal short, second elongate subquadrate, receiving the first recurrent nervure 

 a little before the middle, third quadrate, receiving the second recurrent about 

 the middle ; tegulse black ; legs black, slender, slightly pruinose, calcaria pale ; 

 abdomen elongate ovate, petiolate, petiole black, remaining segments dark ferru- 

 ginous, paler at sides. Length 5.5 mm. 



Hab. — Nevada. One specimen. 



Myrmosa uhicolor Say. 



Male. — Black ; abdomen with cinereous hair ; metathorax with an impressed 

 line ; head with short cinereous hair, somewhat longer about the mouth ; densely 

 punctured ; thorax and scutel densely punctured and with scattered, cinereous, 

 short hair, posterior segments of the former with two light, parallel, impressed 

 lines; wings hyaline, nervures fuscous; metathorax with a longitudinal, im- 

 pressed, very distinct line, and a transverse one at base ; hairs more obvious each 

 side ; punctures smaller than those of the thorax ; abdomen more hairy than any 

 other part of the body. Length three-tenths of an inch (8.5 mm.) (Say.) 



Hab.— N. W. Territory. 



This insect also occurred on the Missouri at Engineer's cantonment 

 and in Pennsylvania. 



Genus 9, METHOCA Latr. 



Male. — Head transverse, flattened in front, convex behind ; eyes 

 ovate, prominent and lateral ; the stemmata large, placed in a tri- 

 angle on the vertex ; antennae filiform, tapering to a point at the 

 apex ; the scape very short ; the joints of the flagellum beyond the 

 third subarcuate ; thorax oblong, the collar extending to the inser- 

 tion of the wings ; the metathorax obtuse ; the anterior wings with 

 one elongate marginal cell, which is pointed at its apex and extends 

 nearly to the tip of the wing ; three submarginal cells, the first as 

 long as the two following, receiving the first recurrent nervure ; the 

 second quadrangular, receiving the second recurrent nervure ; the 

 third extending to the apex of the wing ; abdomen linear, the seg- 

 ments subcrenate ; the hypopygium produced laterally into two ver- 

 tical plates, arcuate at their extremity, beneath produced into a long, 

 recurved, acute spine. 



Female. — Head subglobose ; eyes ovate and lateral ; the stem- 

 mata placed in a triangle on the vertex ; antennas filiform, inserted 



