GALLS CAUSED BY GALL-WASPS 
35 
582 eggs.” The “ fly ” often attacks the buds so fiercely 
that the tissues are destroyed and no gall results; but 
where her zeal has been tempered with discretion the bud 
begins to swell about the beginning of May. Gall forma¬ 
tion proceeds rapidly, and by the end of the month the 
“Oak-apple” has arrived at maturity (Plate IV., Fig. 1). It 
is usually solitary, but sometimes three or four may be 
found together. It is greenish-yellow at first, and soft and 
sappy, becoming harder and tinted rose colour at maturity. 
The larval cavities are numerous, and many of them contain 
parasites, this gall being exceptionally prone to attack by 
many species. The wasps (Biovrhiza pallida , also known as 
Teras terminate) emerge in July. Both sexes are present; 
the male is winged (Fig. 3), the female wingless (Fig. 4), or 
provided with rudimentary wings. She much resembles 
her mother, but is smaller. Adler proved by experiment 
that she crawls down the trunk and pierces the roots. The 
presence of the larvae therein gives rise to the root-galls 
already described, and so the generations are repeated. 
Some females appear to inherit the instincts of the mother 
instead of the grandmother, pricking leaves and buds instead 
of roots ; the galls that result are, however, always abortive. 
The root-gall, it may be observed, yields no inquilines, and 
but one parasite. 
An Oak sprig bearing an “apple” was worn on May 29 
to commemorate the return of Charles II. to England on 
that date (his birthday), and his escape after the Battle of 
Worcester. The custom still survives in some parts of the 
kingdom. Excepting in minor details, the life-history of 
the “ Oak-apple ” gall-wasp is the same as that of all in 
which the regular alternation of generations occurs. The 
larvae of the parthenogenetic winter brood develop in more 
or less hard galls of slow growth (subterranean in two 
species); the larvae of the sexual summer generation develop 
in soft sappy galls of rapid growth. The soft galls are 
produced in spring, when the supply of sap is abundant; 
the harder galls arise in autumn, when there is diminished 
