no. 1834. NEW SPECIES OF STREPSIPTERA— PIERCE. 501 



PSEUDOXENOS ROBERTSONI, new species. 



Host. — Odynerus (Ancistrocerus) Jiistrionalis Robertson, Carlinville, 

 Illinois. Described from one female collected August 27, by Charles 

 Robertson. 



Female. — Length of cephalothorax 1.04 mm., breadth 1.05 mm., 

 breadth of head 0.85 mm., distance between mandibles 0.20 mm. 

 Cephalothorax light orange brown, with a very dark narrow margi- 

 nal line and a dark line behind the opening of the brood canal, the 

 color shading off from these dark lines to a very light disk, apex 

 light, area of spiracles light on the dark rim. Cephalothorax con- 

 stricted at base convex at widest point behind spiracles, convex 

 with slight sinuations to apex which is evenly rounded; spiracles 

 barely attaining the margin; mandibles with a very acute tooth on 

 the inner apical angle. 



Type— Cat. No. 13706, U.S.N.M. 



PSEUDOXENOS TIGRIDIS, new species. 



Host. — Odynerus (Ancistrocerus) tigris Saussure, Carlinville, Illinois. 

 Described from one female collected by Charles Robertson on Sep- 

 tember 23. 



Female. — Length of cephalothorax 0.76 mm., breadth 0.70 mm., 

 breadth of head 0.58 mm., distance between mandibles 0.16 mm. 

 Cephalothorax light brown, darkest on margins, apex light, disk 

 light orange brown. Cephalothorax oval, constricted at apex, 

 broadest behind spiracles, sides convex from base to apex, very 

 even, apex evenly convex; spiracles barely reaching margins, indi- 

 cated by clear round area; mandibles small, oblique with a small 

 outward curved tooth on inner apical angle. 



Type.— Cat. No. 13707, U.S.N.M. 



Genus TACHYTIXENOS, new genus. 



Type of genus. — T. indicus, new species. 



The only species of this genus is a parasite of Tachytes and the genus 

 is at present confined to Asia. 



Male. — Head transverse, broadly produced over antennae. Man- 

 dibles curved, stout, ensiform, apically acute, maxilla? two-jointed, 

 the first joint stout subclavate, the second longer, tapering but not 

 acute at apex. Eyes large, many-faceted. Antennas normally 

 xeniform, rami flattened. Pro thorax transverse, slightly arched for- 

 ward. Mesothorax shorter, emarginate by prsescutum; elytra slen- 

 der, clavate. Metathoracic prsescutum keystone-shape; scuti broad, 

 angularly produced over base of wings, narrowly separated by pedun- 

 cle of scutellum; scutellum reaching prsescutum in a pedunculate 

 process which widens to the main body in a sinuate curve, posterior 

 angles laterally produced, posterior edge bisinuate; postlumbium of 

 different consistency from other parts, with both anterior and pos- 



