REVISION OP STREPSIPTERA — PIERCE. 133 



Acroschismus, differing from the former in wing venation and from 

 the latter in genitalia. The antennae taper as in Xenos. The oede- 

 agus is not bounded at its base by reflexed lobes, is basally bisulcate 

 and apically cleft. The wings have seven primary veins from the 

 base, with one unattached distal vein between the radius and medius 

 and one between the medius and cubitus. 



The genus is parasitic upon Polistes and is confined to North 

 America. 



1. Palpi with first joint longer than second peckii Kirby. 



i. SCHISTOSIPHON PECKII Kirby (1813). 



Xenos vespae Peck in correspondence. 

 Xenos peckii Kirby, 1813. 

 Schistosiphon peckii Pierce, 1908. 



Host. — Polistes fuscatus Fabricius; near Cambridge, Massachusetts 

 (pi. 5, figs. 5,6). 

 The original description by Kirby is essentially as follows: 

 Male. — Dark fuscous, antennae with rami subterete, dilutely albo- 

 punctate, anus pallid, legs yellowish, tarsi fuscous. Length lh line 

 (0.15 inch); breadth of head at eyes, 0.04 inch, length of antennae 

 0.045 inch. Body dark fuscous, minutely pubescent, velvety. 

 Head between antennae longitudinally elevated and almost carinate. 

 Maxillae longer than their palpi, fuscous, minutely white pubescent, 

 subdiaphanous. Thorax with postscutellum longitudinally and 

 transversely canaliculate; postlumbium pale. Wings whitish cine- 

 reous; margin thickened, veins black. Legs cinereous or dusky; 

 tarsi darker. Abdomen more obscure than the rest of the body; 

 anus pale rufescent. 



12. VESP^XENOS, new genus. 



Name derived from Vespa (the host genus) + Xenos (the original 

 genus of wasp parasites), meaning a xenid parasite of Vespa. 

 Type of genus. — Vespaexenos crabronis, new species. 



a Male. — X. nigro-fuscus, antennis; ramis semiteretibus dilutioribus albo puncta- 

 tis, ano pallido, pedibus luridis; tarsis fuscis. Long. corp. 1| lin. (Professor Peck's 

 measurements of fresh specimens: Length of body 0.15 inch, breadth of head at eyes 

 0.04 inch, length of antennae 0.045 inch.) Corpus nigro-fuscum, ex pube brevissima 

 et nisi sub lente forti omnino inconspicua opacum et quasi velutinum. Caput inter 

 antennas longitudinaliter elevatum et fere carinatum. Palpi articulo primo secundo 

 longiori. Antennae capite longiores; ramis magis dilute fuscis, subdiaphanis, punctis 

 minutissimis albis, et, uti suspicor, hexagonis, nisi sub lente forti vix conspicuis 

 irroratis. Truncus. Thorax postice in medio obtusangulus. Scutellum longitudi- 

 naliter et late canaliculatum. Postlumbium pallidum. Alae cinereo-albidae; mar. 

 gine crassiori, nervisque nigris. Pedes cinerei vel potiiis luridi; tarsis nigricantibus. 

 Abdomen reliquo corpore magis obscurum; ano pallide rufescentii (Kirby, 1813). 

 84359— Bull. 66—09 10 



