Hymenoptera aculeata collected in Algeria: the Sphegidae. 65 
Africa, and differs considerably in general appearance 
(colour, silvery pilosity, etc.) from the more European- 
looking fauna of the coast. As a rule, in these “Saharan” 
forms, the prevailing colours are pale lemon-yellow, creamy- 
white, and red (or testaceous) with very little black, 
blended harmoniously together, and with the contrasts 
between them further softened and disguised by their 
silvery clothing ; whereas of the “‘ Kuropean” forms, some 
exhibit strong contrasts of black and red, others of black 
and yellow, and many (generally small species) are simply 
black. On the other hand, it is puzzling to find (along 
with the gaily-coloured yet evidently “cryptic” Saharan 
forms, and confined to the districts frequented by them) 
a certain number of very large, quite black (or black with 
silvery hair-patches), and altogether most conspicuous 
insects, usually with the wings very dark also—belonging 
to many different genera in which such a coloration is 
quite abnormal or even unknown in Europe, though 
apparently yet further south than the Sahara it is not 
uncommon. 
Of the genera which occur both in Europe and in North 
Africa, some (as might be expected) are represented by 
many more species in the former, others in the latter. 
Thus the timber-frequenting Sphegidae, such as Try- 
poxylon, Crabro (groups of Crossocerus, ete.), Passaloecus, 
Pemphedron, etc., figure little in the list of Mr. Eaton’s cap- 
tures, and scarcely at all in my own; though this, perhaps, 
is partly because of a collector's natural tendency to be 
attracted by striking and conspicuous insects and to 
neglect such as look to him ordinary and uninteresting. 
On the other hand, of certain sand-burrowing genera, 
e.g. Ammophila, Stizus, and Cerceris, the Algerian species 
are both exceedingly numerous and far more diversified 
in appearance than would be expected by a Hymenopterist 
familiar only with European forms. It might be supposed 
that the same would be the case with Mellinus, but as a 
matter of fact neither Mr. Eaton nor myself encountered 
that genus in Algeria at all. Our captures of Gorytes 
include several very beautiful or otherwise remarkable 
forms, but hardly any of the numerous rather common 
and deceptively similar species which figure so largely in 
the European fauna. 
Both Tachytes and Tuchysphex are represented in Algeria 
by many remarkable species. Some of the finest are 
TRANS. ENT. SOC. LOND. 1911.—PARTI. (MAY) F 
