304 MODERN CLASSIFICATION OF INSECTS. 
the bare supposition that it infests Halictus, the type H. Curtisii 
having been found in company with the males of Halictus wratus, on 
the 15th of August, in one of which he found a pupa exactly at the 
apex of the abdomen. (See Dale, in Mag. Nat. Hist. July 1830.) 
The genus Xenos is restricted to the wasp genus Polistes, X. vesparum 
(Rossii A.) attacking P. gallica, and the American X. Peckii infesting 
P. fuscata. Rossi also mentions Vespa sexfasciata, and some other 
more minute species, as infested with a similar foe. Mr. Kirby found 
exuviz in V. concolor, an exotic species of the restricted genus Vespa. 
(Sowerby, Brit. Miscell. 45.) The Senator Van Heyden has ob- 
served a new species of Xenos, in which the branches of the antenne 
are of unequal length, in Polistes gallica, and another species much 
smaller than X. Rossii, in a species of Odynerus (O. auctus?). M. 
Van Rozer had also observed the larva of a species of this genus in 
the body of Vespa vulgaris. (Trans. Ent. Soc. vol. i. p. Ixxiv.) Mr. 
Shuckard also possesses other exotic species of wasps similarly infested. 
Mr. Templeton found a specimen of Elenchus tenuicornis (Walkeri ?) 
in his net, in which he had placed the nest of a Bombus, whence he 
thought it probable that it was parasitic on that genus; but having 
discovered another species in the Mauritius, where the genus Bombus 
does not occur, he is now inclined to doubt his former opinion. 
(Trans. Ent. Soc. vol. i. p. 174.) The Mauritian species he considers 
to be probably parasitic upon a species of wasp (Polistes ?) which is 
frequent in that island. M.L. Dufour has also observed a larva, 
evidently of one of these insects, with the head exserted between the 
abdominal segments of one of the Fossorial Hymenoptera, Ammophila 
sabulosa (Aun. Sci. Nat., Jan. 1837, p. 19.); and Mr. R. Temple- 
ton captured a species of Sphex at Rio Janeiro, from the abdomen 
of which he extracted a new species of Xenos, which he has named 
X. Westwoodii, and of which he has forwarded a detailed descrip- 
tion and figures to the Entomological Society of London. 
The species seem widely distributed, although, from their minute size, 
they have hitherto escaped the observation of collectors abroad. The 
genus Stylops, of which there appear to be many species (of which suf- 
ficient comparative characters have not yet been given), has hitherto 
been found only in England, if we except S. Childrenii Gray, dis- 
covered in a North American bee; Xenos occurs in the middle and 
south of Europe, and in North America; X. Westwoodii was found 
in a Brazilian Sphex; Elenchus in England, as well as in the island 
of Mauritius ; R. Templeton having captured many specimens of an 
