266 Mr. P. Cameron on new 
(Sula jiber); two males from Abd-el-Kuri, near Socotra, 
23.11. 1899 (W. BR. Ogilvie Grant), “ from Sula sula” ; two 
males from Christmas I. (4.IL.8. ‘ Flying-Fish’) ; one male 
and two females from Adele I., N.W. Australia, 2. v. 1891 
(J. J. Walker, R.N.). 
For remarks on the association of this species with the 
frigate-bird (fregata aquila, L.) and its wide distribution, 
see Speiser, Zeitschr. f. syst. Hym. u. Dipt., u.Jahrg. Heft 3 
(1 May, 1902), pp. 146-147. It is stated by Speiser (Joc. cit. 
p- 147) that the fly met with by Darwin on St. Paul’s L., 
Atlantic Ocean *, evidently belongs to this species. The two 
specimens obtained by Darwin on this remote islet are in the 
British Museum collection, and were doubtfully referred by 
Walker (List Dipt. iv. p. 1143) to Ornithomyta (Hippobosca) 
nigra, Perty (Del. Anim. Art. p. 190, pl. 47. fig. 15), which 
is in reality a Pseudolfersia. It seems to me that Walker’s 
provisional determination is correct, and that Darwin’s speci- 
mens really belong to Pseudolfersia nigra, Perty, which is 
very possibly merely a synonym of Pseudolfersia spinifera, 
Leach. Nevertheless, I prefer for the present to keep the 
two supposed species distinct, especially since Darwin’s speci- 
mens, in addition to being smaller than the average size of 
Ps. spinifera, are algo in bad condition. 
XXIII.—On some new Genera and Species of Parasitic Hy- 
menoptera from the Khasia Hills, Assam. By P. Cammron. 
J OPPINI. 
ACHAIUS, gen. nov. 
Apex of abdomen bluntly pointed; the keel on segments 
1-4. Mandibles unequally toothed, the upper much larger 
than the lower. Clypeus not distinctly separated from the 
face, its apex transverse. Labrum projecting. Scutellum 
convex. Median segment completely areolated, its apex 
with an abrupt oblique slope; the areola distant from the 
base, large, longer than broad, extending to the top of the 
apical slope; it is bluntly rounded behind, its apex slightly 
rounded backwards. The sides of the segment bear stout, 
longer than broad, teeth; the spiracles linear. Legs longish, 
* Cf. Darwin’s ‘Journal’ (ed. 1889), pp. 7-10: the geographical 
position of St. Paul’s I., on which the booby and the noddy were the only 
birds found, is 0° 58’ N. lat., 29° 15’ W. lone. 
