Hymenoptera aculeata collected in Algeria: the Sphegidae. 67 
particular plants which are most likely to reward special 
observation. And to take the particular case already 
alluded to, there can be no doubt that the simplest way to 
ensure a magnificent series of the handsomest Algerian 
Hymenoptera—I do not say the best way of securing 
really important scientific results—is to spend day after 
day of long hours of sunshine among the almost mono- 
tonous patches of Ammi visnaga which fill the Oued of 
Biskra in the months of May, June, and probably July in 
a favourable year. No skill is required in taking the 
insects under such circumstances, and the only difficulty 
is to make the work of determining and preparing the 
specimens keep pace with the endless stream of fresh 
captures. 
A matter to which I should like to invite attention is 
the great length of the period throughout which certain 
species appear to be on the wing annually in Algeria, 
examples of them having been taken in almost every 
month of one year or another. Few, if any, Sphegidae 
appear in our own country for more than a few months; 
and most of them are rather summer or autumn than 
spring insects. That a species should appear earlier in 
Algeria seems natural enough, but one would rather expect 
it to be also “over” earlier, which apparently is seldom 
the case. It looks as though, in some cases, two or even 
three generations of the same species must be produced 
within a year; for several of the specimens taken at quite 
late dates (August or September) are in as fresh a condi- 
tion as or even fresher than earlier ones. At the same time 
many species, and among them some of the most char- 
acteristically Saharan forms, seem, from the dates here 
recorded, to have a comparatively short season—generally 
appearing first towards the end of May and becoming 
plentiful a week or so later, but not occurring in the spring 
or the late autumn. As these records extend over six 
successive years, statistics founded upon them may have 
some value; but they would of course be more reliable if 
Mr. Eaton or myself had spent longer periods than we 
did on any single hunting-ground, or had continued 
indefinitely to secure further duplicates of species which 
we had already taken “to satiety.” Probably hymeno- 
pterists who are fortunate enough to reside in Mediter- 
ranean countries could supply information on these matters 
which would be interesting to those who can only visit 
F2 
