A LARVA PLAGUE IN DEFFER WOOD, YORKS. 
B. MORLEY, 
S kelm a > ithorpe , H udders field. 
For some years a few species of Spring-feeding larvae have been 
so numerous in Deffer Wood, near Skelmanthorpe, that by 
mid-June they have completely eaten up all the foliage. 
The first defoliation took place in 1910, and since then it has 
yearly become more complete, but it is hoped that the plague 
has now ceased. Probably the shortage of food for the growing 
larvae has had disastrous results not only on the species that 
caused the devastation, but especially on other species of 
tree-feeding lepidoptera that are seldom more than common. 
During 1909, the year before the first swarm, my records 
of the appearances of the species that caused it are as follows : — ■ 
Phigalia pilosaria common. 
Himera pennaria common. 
Hybernia defoliaria common. 
H. aurantiaria plentiful. 
Oporabia dilutata abundant. 
Cheimatobia boreata abundant. 
C. brumata abundant. 
Tortrix' viridana abundant. 
During the early summer of 1910 all the above species took 
about an equal share in the first defoliation, and as the food 
supply was consumed before all the larvae pupated, it was 
apparent that a keen struggle for existence would take place. 
Singularlv enough, Tortrix viridana was the first species to 
fail. From great abundance in 1909 it fell to almost extinction 
by 1912. The rapid disappearance ot this species may be 
accounted for by the fact that the foliage of the oak was first 
eaten up, and the species being an oak feeder, its food supply 
failed before the larvae completed their growth. 
Cheimatobia boreata also quickly diminished in numbers. 
In 1912 it almost failed to appear in the perfect state — being 
strictly a birch feeder, the larvae would perish if not full fed 
when the birch leaves had all been eaten up. 
Oporabia dilutata gradually showed a reduction in numbers. 
It was abundant in the perfect state in the autumn of 1910, 
but it has appeared since in greatly reduced numbers. Last 
autumn (1913) it was scarce. 
All the other species in 1912 were most abundant as larvae 
with the exception of Phigalia pilosaria. In the early months 
of the year the emergence of this species showed a great 
falling off compared with the abundance of the previous year, 
and the resulting larvae were not plentiful, and they apparently 
fared badly. In 19x3 the emergence was a poor one, while 
during the present year the moth has been a rarity. 
Himera pennaria was the next to fail. It was very abun- 
dant in the perfect state during the autumn of 1912, and the 
larvae in the spring of 1913 swarmed, but curiously, in the 
1314 May 1. 
