120 BULLETIN 66, UNITED STATES NATIONAL MUSEUM. 



Male. — Typically xenid in the possession of four-jointed antennae, 

 four-jointed tarsi, and two-jointed maxillae. Species of this genus 

 differ from Scliisto siphon (Xenos) peckii Kirby in the cleavage of the 

 ninth segment of the abdomen to form two claws, between which the 

 reflexed cedeagus arises, and in having the tip of the cedeagus 

 simple, not cleft, with the genital pore before the apex. A charac- 

 teristic of the genus is the presence of the mesostigmatal lobe on the 

 mesothorax. 



Female. — Cephalothorax not as a rule abruptly narrowed behind 

 the stigmata! angle, elongate trapezoidal, obtuse or truncate at apex. 

 Stigmata seldom laterally prominent. Mouth ventral with mandi- 

 bles on each side, rather broad and obtuse. Abdomen with four 

 median genital canals on second to fifth segments. 



Triungulinid : Body oblong, slightly narrowing posteriad. First 

 eight segments normal, ninth greatly elongate, deeply emarginate for 

 tenth, which is elongate and terminated by two stylet bearing lobes, 

 contiguous at base. 



The genus contains the following species: 



1. hubbardi Pierce, parasitic on Polistes crinitus (americanus) ; 

 Florida. 



2. bruesi Pierce, parasitic on P. metricus; Michigan. 



3. nigrescens Brues (1903), parasitic on P. rubiginosus; Texas, 

 Louisiana. 



4. pallidus Brues (1903), parasitic on P. annularis; Texas, Dis- 

 trict of Columbia, Florida. 



5. pecosensis Pierce, parasitic on P. texanus, rubiginosus; Texas. 



6. wheeleri Pierce, parasitic on P. metricus; Connecticut, District 

 of Columbia. 



7. bowditcM Pierce, parasitic on P. pallipes; Massachusetts, Ohio. 



8. liunteri Pierce, parasitic on P. new species, near minor; Texas. 



9. texani Pierce, parasitic on P. texanus: Texas. 



10. rubiginosi Pierce, parasitic on P. rubiginosus; Louisiana. 



11. marimus Pierce, parasitic on P. rubiginosus; Texas. 



Key of males. 



1. Wing venation pale except at costal margin 2. 



Wing venation dark and distinct throughout , 7. 



2. Palpus indistinctly separated from maxilla nigrescens. 



Palpus distinctly separated 3. 



3. Second antennal joint set very deeply in first hubbardi. 



Second antennal joint not set very deeply into first 4. 



4. Apex of cedeagus turned upward almost at a right angle 5. 



Apex of cedeagus turned upward at an acute angle C. 



5. Palpus considerably shorter than maxilla liunteri. 



Palpus about equal to maxilla bruesi. 



6. Radius of wings not interrupted at node pallidus. 



Radius of wings interrupted at node pallidus texensis. 



