OCCASIONAL ABUNDANCE OF INSECTS. Gey 
their physiology, habits as imagines, or food as larvee, any 
good reason why one should appear with the regularity of 
the Hast wind and the other but twice or thrice in a 
lifetime. I mention this case, because it was’perhaps so 
to speak one of the most dramatic on record, but the 
entomologist knows that hardly a year passes without 
some such exceptional manifestation, sometimes a lady- 
bird, sometimes a hawk moth. No doubt it will be 
remembered how some years ago on the hills near Clitheroe, 
appeared armies of the larve of the Antler Moth Chareas 
gramuvis, how like an Hgyptian plague they suddenly 
became manifest devastating the grasslands, and how 
they disappeared with the celerity of the frogs and of the 
lice. Again in 1879, one of the coldest and wetest years 
of this century, a butterfly Vanessa cardw, and a day 
flying moth Plusia gamma literally swarmed not only over 
the whole of the Continent but also all over Great Britain 
from Wick to Penzance. And even this summer we have 
just passed through has been marked in red, by reason 
of the unusual numbers of a moth as beautiful as it is 
generally rare, [ mean Devopera pulchella. 
The tale of similar instances might be indefinitely pro- 
longed, but instead of reiterating cases which are but 
examples of the same phenomena, I want to focus 
attention more especially on one particular species of 
insect which perhaps more than any other has attracted 
. the notice of entomologists by reason of the remarkable 
irregularity of its appearances and the profundity of its 
disappearances. ‘The species I refer to is the hawk moth 
Detlephila galw, so called because its larva feeds on the 
Galiwm or yellow bedstraw. This moth is distributed 
generally but sparingly over Hurope, more frequently in 
the South, and is found also in Asia and North America. 
Now the butterfly Colias edusa of which I spoke, 
