OF THE HIND WINGS OF HYMENOPTEROUS INSECTS. 135 
cases losing the re-curve as they approach the apex of the wing), I should, in ill-defined 
cases, call any straight hook at the commencement of the distal a sub-basal hook. Thus 
in Pterygophorus I should reckon three (fig. 8), although there is nothing but the form of 
that nearest the distal, and the fact of the scars beginning nearer the base than is usual 
with distal hooks, to separate them. 
Allantus scrophularius has 5, on the costal nerve, at wide intervals, nearer the distal hooks than the 
base. 
Allantus (N. America) (fig. 1 a), 6 or 7- 
Tenthredo Nothus, 5 well-marked sub-basal hooks, beginning near the distal ; but the series is con- 
tinued almost to the base in the form of a deflexed hair, with a large scar on the lower edge of 
the costal nerve. The other hairs have not such u scars. 
o 
Tenthredo viridis (fig* 9 a), 12. 
Tenthredo viridis} 2. 
Sciapteryx, 4. 
Hylotoma ustulata, 3. 
Hylotoma femoralis, ? 
Cephus pygmteus, 6, about midway between the base and the distal hooks. 
Xyphidria Dromedarius has 7 prominences (fig. 12 a), close to the base of the wing, on one of which 
is a large sub-basal hook. Probably 6 others have fallen off. 
Fore Wings.— The folding over of the lower margin of the fore wing, for the rccepi ion of 
the hooks of the hind wing, varies much in different insects, in form, size, arrangement, 
and in texture, that part of the wing often differing greatly from the rest of the membrane, 
as in Pelecmus polycerator, where the principal roll is thick and dark, and thickly studded 
with short stiff spines or hairs, while the membrane of the wing is clear and thin, having 
large fine hairs at wide intervals. It is frequently serrated, or edged with short stiff hairs, 
along the npper part ; sometimes it takes a second fold, when the serration usually ceases 
{&&m.Astata Boops). 
In some insects, as in all the Tenthredinim which I have seen, in Scolia, Mutilla, and 
Stilbum, there is but one roll ; and in some (as Mutilla) it becomes very narrow, and 
extends almost to the base of the wing. 
In Vespa the roll for the distal hooks is very broad, and doubled, and there is a second 
and narrower roll, nearer to the base, for the sub-basal hooks. 
In Chlorion the roll is broad at the centre of the wing, diminishes and widens again as 
it approaches the base, and there is a short broad turning up of the wing quite at the base. 
InPimpla, Paniceus, Tryphoti, Mesostemis, and Pelecinus there are two separate rolls. 
In Ophion two, or one prolonged roll. 
(Query. — Is it always a roll ?) 
Xyphidria Dromedarius has some hairs on the costa, near the base of the fore wing, much 
resembling in appearance the sub-basal hooks in the same part of the hmd wing. 
The only genus of four-winged insects, not Hymenopterous, on the hmd wings of which I 
have observed a hook, is Aphis * (Tab. XVI. fig. 13 «). It is found in all the British species 
of that genus described by Mr. Walker, of which there are specimens mounted by him in 
Mr. Westwood bavin* suited to Dr. Gray that the hook of the Aphides was figured and described by Messrs 
Ratzeburg and Curtis, he 
with the followin. 
eburg, in his < Die Forst-Insecten/ figures four species of Aphides in their various 
