OCCASIONAL ABUNDANCE OF INSECTS. OT 
early summer in Italy and all the South of Kurope and 
like an inverted Gothic invasion, steadily ceaslessly the 
northward march, or rather flight, went on all through 
that year till the last of their armies died out in late 
autumn discolouring the Scandinavian snows. 
Now that remarkable flight is an ascertained fact, and 
although I do not maintain that those same identical 
insects which broke their pupal envelope on the plains of 
Lombardy or on the African shore ever reached the Baltic 
coasts, or indeed did much more than flutter helplessly to 
earth a few hundred miles from their native thistle, yet 
the decimated regiments were filled up by ever fresh 
recruits and the general impression given was a northward 
progress of incalculable host of Vanessa cardut. 
Now the reason of the emergence in that particularly 
inclement year of all these butterflies, the reason of their 
northward flight, or any flight at all, I am not concerned 
now to explain. My point is rather, that it is most un- 
scientific, most unjustifiable to assume that the causes 
which made the Sphinx moth Deilephila gali plentiful in 
certain spots round the English coast in 1870 and 1888 
must necessarily or even probably be the same as, or 
similar to those which induced these prodigious flights of 
Vanessa cardwi all over Hurope in 1879. We must judge 
each case on its own merits. Consider then the differ- 
ence; cardut is a strong winged day flying butterfly of 
particularly robust constitution whose larve feed on thistles 
principally, a herb common wherever the foot of man has 
trodden. 
Deilephila gal is a delicate hawk moth only flying 
during the dusk whose larve feed so far as is known only 
on the bedstraw and the willow herb, plants narrowly 
restricted in area of growth and far from common anywhere. 
The flights of cardu are visible, notorious; they settle on 
