118 BULLETIN 66, UNITED STATES NATIONAL MUSEUM. 



Female. — The principal character of the species is the mandible. 

 This appendage is very broad at base, with two lobes, to the outer of 

 which one set of muscles is attached. At the middle of the concave 

 base another set of muscles is attached. The forward or outer angle 

 is toothed, acute, the inner angle is lower and rounded. 



The following description by Nassonow is taken from a translation 

 in manuscript in the library of the Bureau of Entomology: 



Triungulinid : Size never more than 0.25 mm. in length. Body ventrally flattened, 

 dorsally convex, narrowed at ends and widened at middle. Color, bright cinnamon; 

 with side of head at eyes and sides of last abdominal segment black. Head somewhat 

 triangular, with rounded angles. Five simple eyes at lateral angles. Antennae and 

 sutures absent. Head above hard, chitinous; below soft, transparent and provided 

 anteriad with two small bristle-bearing protuberances. Mouth parts very incom- 

 pletely developed. Mouth opening above bounded by the border of the upper wall 

 of the skull and below by a strip which passes over without definite limits into the 

 lower wall of the skull. Thus differentiated upper and lower lips are absent. The 

 only pair of mouth appendages corresponds most probably to the mandibles. These 

 appendages are seen outside only through the thin and transparent wall of the lower 

 part of the head and have the appearance of sticks bent toward the longitudinal axis 

 of the body. The thorax consists of three distinctly delineated segments and is slightly 

 narrowed toward the front. These segments are longer than the abdominal. The 

 dorsal segments bear figures of the shape of three or four transverse rows of quadrangles 

 of irregular outline. These dorsal sclerites bear each a pair of bristles near the posterior 

 margin. The pronotum is also armed with a pair near the anterior margin. The 

 ventral sclerites are but slightly convex at the middle, and on the sides at the pos- 

 terior margin of the convexity of each segment is attached a pair of legs. Between the 

 bases of the legs are regular rows of bristles. The basal member of each leg is strongly 

 widened and is so joined with the thorax as to be slightly movable. Its opening for 

 the reception of the femur is very large and is directed obliquely forward. On its 

 anterior margin it bears a more or less obtuse tooth near which are situated three 

 round bristles with a ring-shaped shaft at the base. Femur basally enlarged, joined 

 by very free, movable articulation with preceding joint. Tibia straight, narrow, 

 bispinose. Tarsus merely a pulvillus. Abdomen consisting of ten distinct segments, 

 the first eight of nearly equal length and gradually narrower posteriorly. Dorsal scle- 

 rites armed near sides of apical margin with spine. The ninth dorsal longer than 

 preceding; posterior margin with semilunar excavation ; near sides of posterior margin 

 armed with spine. Ninth ventral apically bearing two conical bristle-tipped append- 

 ages. Last segment very narrow apically; posteriorly bearing very long styloid proc- 

 esses; dorsally near sides of apical margin with bristles (Nassonow, 1892 e). 



2. XENOS JURINEI Saunders (1872). 



Xenos vesparum Jurine 1818, 1832, not Rossi. 

 Xenos rossii jurinei Saunders, 1872. 



Host. — Polistes gallicus Linnaeus; Geneva, Switzerland (pi. 5, fig.. 3). 



The following description is abbreviated from the original descrip- 

 tion by Jurine. 



Male. — Head flattened in front. Mandibles long, yellowish, 

 slightly arcuate, crossing in front of mouth. Maxillae pubescent, 

 subequal with the palpi, which latter are subulate. Eyes large, oval, 

 very prominent, many faceted. Antennae with third joint laterally 



