ABUNDANCE OF PLUSIA GAMMA AND VANESSA CARDUI. 161 
note that V. cardui and P. gamma have been more than usually 
common; as a rule V. cardui is rather a rare insect in this 
neighbourhood (Herefordshire). We first noticed them about 
three weeks ago” (i.¢., about 26th May). Going farther north, 
near Rotherham, Yorks., on ‘‘May 28th, June 2nd and 7th, 
P. gamma was unusually abundant; one field we passed for a 
near cut to the woods was alive with them. V. carduwi is this 
year abundant also; we do not see it every season.” ‘The last 
named is also abundant on the cliffs at Scarborough, Yorks. 
From Perthshire I learn that, owing to the very unfavourable 
weather, V. cardui has not been seen at all, and P. gamma only 
very sparingly; but in Sutherlandshire ‘‘ P. gamma occurred 
pretty freely at flowers of Arctostaphylos uva-ursi, and even on 
the top of Ben More and Canisp, over 3000 ft. ; it struck me as 
rather curious then, since I have seen them more commonly here 
(Invershin), but certainly not in any way swarming; I saw about 
fifty at sugar one night, by far the commonest moth that par- 
ticular night. I have notseena single V. cardut, although I have 
been well over the country, forty or more miles, and well on the 
coast; so they have not reached here yet.” And still farther 
north, in Shetland, we find P. gamma in unusual numbers. ‘I 
first saw P. gamma about the beginning of this month (June) ; I 
believe it was on the 3rd. In former years I have only taken it 
on the cliffs, but this year I have met with it from the water’s 
edge to the tops of the highest hills (900 ft.), but not by any 
means common. Owing to the spell of bitterly cold north-east 
wind we have had they have been checked, if not killed; it is 
fully a week now (16th) since I saw one. I have seen no V. 
cardui up to date; if I remember rightly, the end of this month 
is the time for them here.” 
So far as I can learn, neither species was particularly common 
last autumn ; undoubtedly some few P. gamma were to be found, 
but in my own experience their number was below the usual 
autumn average ; and of V. cardui, I did not see a solitary one, 
nor did we find any abundance of either species during the warm 
weather of this spring, April 2nd to 10th, when the shade tem- 
perature touched 74°; or the warm days later in that month and 
the earlier part of May, when they would surely have been 
tempted from their winter quarters had they been hybernating. 
I have little doubt that the abundance of both species recently 
noted is due directly to the agency of migration; in other words, 
that the individuals comprising it are themselves immigrants, 
which may, under favourable conditions, be the forerunners of a 
still greater abundance in the autumn. ‘The subject is, however, 
one of too deep an interest to be dismissed with a few hasty 
remarks, founded largely upon scattered fragments of evidence ; 
and it is in the hope that entomologists, not only in this country, 
but in those other countries similarly affected to our own, may be 
