THE SWISS SPECIES OF THE GRHNUS HESPERIA. 51 
and finally, alveus is single brooded. These are well known facts, and 
throughout these notes I have made it a point, as much as possible, to 
avoid descriptions of typical forms, but in this case it was necessary ; 
for both species in question vary on similar lines, and so two aberra- 
tions are often best distinguished by the differences which mark the 
types. Alveus, strange to say, rarely produces aberrations suggestive 
of armoricanus, a specimen reduced in size being extremely rare ; but 
the latter frequently approaches alvens. (These will be mentioned in 
notes on aymoricanus.) - From the remaining species, typical alveus is 
easily distinguished, only with the following aberrations will any 
difficulty arise. The form in which the central spot of the median 
band on the underside of the hindwings, projects towards the base of the 
wing, thus assuming the characteristic feature of the B. group species, 
is not very uncommon ; but it is, as previously noted, quite the most 
important form of variation occurring in the genus, for, with one 
exception, I have found it in every species. of the A. group, and no - 
matter what the species, a specimen of this form usually resembles 
some member of the B. group. The extent to which the projection 
from the central spot towards the base of the wing is developed, varies 
in alveus indefinitely ; ranging from a mere excrescence, just sufficient 
to break the straight edge of the band, to a well pronounced tooth, half 
as long as the spot itself. I have never seen it of exactly the same 
formation in any two specimens, a feature worth noting for purposes 
of identification ; as in group B., this projection has a more or less 
distinctive formation in each species. ‘To this form of variation I give 
the name extensa, for it is found throughout the group in the form of 
more or less pronounced aberrations, which in themselves it would be 
useless to name, as they never develop the same formation twice in any 
given species. However, in order to avoid a great amount of repeti- 
tion with each species it is necessary to name the form of variation, 
and I do so in a collective manner, to cover it in all stages of develop- 
ment, the diagnosis being, any aberration of an A. group species, pre- 
senting to a greater or less extent, the features of the median band 
(underside hindwing) characteristic of group B. Conversely, I give 
the name reducta to those aberrations of the B. group species which 
assume the even inner edge to the median band, as in group A., or have 
their typical markings so modified as toapproachit. The ewtensa forms 
of alveus are to be found wherever the species occurs. | have taken more 
than a dozen of these aberrations both in the lowlands and mountains, 
in the Valais, Bernese Oberland, and Grisons, and I must acknowledge 
having recorded as onopordi, in the Entomoloyist for 1911, such aber- 
rations of alveus, which I had taken in the Pyrenees. I can only hope 
that my record has not misled many collectors in the past; and add 
that at that time I was not acquainted with genuine onopordi, the only 
condition which could have made such a mistake possible, for with its 
much greater size, and totally different character of markings, alveus 
never can be said in the least to resemble onopordi. There is one 
species which some of these aberrations must resemble very closely, 
namely, numida. It does not come within the sccpe of this paper, but 
it would be interesting to know if the projection from the ceritral spot 
in that species (?) has a constant formation, which would enable it to 
be distinguished from the fluctuating formations of the ewtensa aber- 
rations of alveus ; especially as there is no difference in the genitalia of 
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