50 | THE ENTOMOLOGIST’S RECORD. 
have lasted for another week or ten days. This would give a period 
of flight of from eight to nine weeks, and exceeds the greatest length 
I have recorded in the plains: six-and-a-half weeks; 7.e., from 
July 18th to September 2nd. My observations, on the whole, lead me 
to think that the abundance or rareness of the insect in a given locality 
is more the deciding factor as to the length of the period of flight, 
than altitude or climatic conditions, though, of course, the latter, 
indirectly, may be said to be partly responsible, in as much as it helps 
to determine the abundance, or otherwise, of the species. The actual 
life of the individual does not last more than half the total period, if 
one may judge by the time which elapses between the first appearance 
of the insect and the first really worn examples seen. Hence, when 
there is a plentiful supply of individuals, three-fourths of which 
probably emerge in the first ten days of their season (which is the 
* moment of greatest abundance), and the remainder continue to emerge 
periodically, we get an extended period of flight. The converse, I have 
noted, too, on more than one occasion. This irregular emergence is 
common to all the species of the genus, in several instances to a much 
greater extent even than shown by alveus. But it should be most 
carefully noted that the irregularity only applies to that fraction of the 
brood which does not appear with the majority, for the first instalment 
of all species of Hesperia appears with the regularity of clockwork. 
So much go is this the case that at any given altitude one can foretell 
what the next species of Hesperia to emerge will be with complete 
certainty. For instance, between 5,000 feet and 6,000 feet, the first 
species of the season met with will be either malvae or malvoides, 
according to the locality, between May 15th and 25th. By the first 
week in June a large species will be noticed—andromedae. About a 
week later two more species appear at different elevations—cacaliae 
and serratulae. Ten days to a fortnight later, by which time the first. 
species will be past its prime, and serratulae flying with the others up 
to 6,000 feet, while they have emerged still bigher, and alveus will 
appear ; or, if it is a locality where carthami occurs, it will precede 
alveus by a few days. About a month will then elapse before carlinae 
puts in an appearance, and about the same time ryffelensis will also com- 
mence. The same regularity will be found at any level, high or low, 
I have tested this repeatedly and never found it otherwise: in the 
plains, too, even the double-brooded species appearing in the most 
perfect rotation. 
The variation shown by alveus, as we at present knee it, is con- 
siderable. Many races are in their extreme form very different, but 
the transitional forms are always numerous. In spite of this, aberra- 
tions of alveus are not often very troublesome to identify. Difficulty is 
only experienced when dealing with aberrations which resem ble species 
very nearly related to alvews, which have, as it happens, all been 
previously treated as varieties of the latter. There are among the 
Swiss members of the genus only two such species, namely: arnrori- 
canus and ryffelensis (for the latter will, I think, undoubtedly prove 
distinct). Armoricanus, though it bears, in a general way, a closer 
resemblance to alveus than any other Swiss species, can always, with a 
little care, be distinguished. Typical alvews is a decidedly larger 
insect, and the white markings are proportionately heavier; the ground 
colour of the hindwings, underside, is not usually so bright in alveus ; 
