274 OAK GALLS AND GALL INSECTS
Parasites attacking gall-making insects belonging to the
Cynipina are chiefly members of the family Chalcididae. These
are small blue or green-metallic coloured Hymenoptera preying
upon both larvae and pupae, the same species being often found
in different galls.
Ichneumonid and Braconid forms, parasitic on the Cynipid
oak gall-makers, are not numerous.
Parasites often prey upon the larvae of Inquilines. Certain
Cynipidae are parasites upon other insects, such as Aphidae, and
are sometimes found in the galls of members of their own
family.
Parasites reproduce themselves sexually. Agamic forms,
are, however, found among Inquilines, the genus Ceroptres
furnishing examples of both kinds.
Protection against Parasites.
Various devices for the protection of the larvae against
these intruders are consequently necessary, and it is on this
account to a large extent that galls present such a variety of
form and structure. Hairs may be produced in abundance on a
gall, as in the case of Andricus ramuli, where it is covered with a
dense white matted growth, or a few stiff hairs may be present
(Neuroterus tricolor). In Andricus fecundatrix, the gall is com-
pletely imbedded in an abnormal growth of scale leaves, giving
it the appearance of a hop. A covering consisting of the phloem
or bast cells of the peripheral layer protects Andricus corticis
galls. In the case of Andricus sieboldii, the gall secretes a sweet
sticky substance, of which ants are very fond, and these latter
insects often protect the galls with a hood of earth. A hard woody
growth near the centre of the gall serves as an extra means of pro-
tection to the larva in the case of Cynips kollari. In other cases
the larva may be enclosed in a separate cocoon within the gall
(Andricus curvator and A. inflator). The substance of the gall may
be" very bitter and obnoxious to birds which peck at it to get at the
larva within (Cynips kollari). Other galls are highly coloured as a
warning to birds (Biorhiza terminalis). The most interesting
form of protection is that of "'Protective Resemblance" where
galls take the likeness of buds so accurately that even when
specially searching for the galls one is liable to pass them
Over without notice (Andricus albopunctata). Parasites often
distort galls either by stunting them or causing them to swell. I