Oak Marble Gall Wasp - Andricus kollari

Alternative names
Oak Marble Gall
Description

Length 1.5 to 2mm. The male wasp is very dark brown to black on the head has a hunched thorax, with a black abdomen. The legs are yellowy brown and the antennae are a translucent yellow/brown colour. The female has a dark brown appearance overall. The gall is seen more often than the adult wasp.

Similar Species

Recently, Andricus infectorius galls have been found on two sites in the Charnwood Forest.  (see Leach,C. 2020 Andricus infectorius (Hartig,1843): Biology, History & its occurrence in Britain. Cecidology 35 (1): 22-26.)

It is very similar to A kollari, described in the above as 'when young, the galls are green with raised pale yellowish bumps . . as they mature they become reddish brown and although the outer surface becomes crinkled and slightly pliable, the galls beneath are extremely hard and woody.'

Sam J Buckton (Cecidology 37 (1): p.13) describes it as having 'a narrowing by the attachment point, and a slight raised ridge connecting the pimples’.

 

Identification difficulty

Adult Gall

Habitat

Anywhere that the host oak is found.

When to see it

Adult females exit Oak Marble Galls from August to October.

Life History

Andricus kollari has 2 generations per year. The first of which is sexual, whereas the second is agamic (all female, and needs no male to reproduce). This wasp also needs two species of oak in which to breed. The sexual gall is found on the buds of the Turkey Oak, whereas the agamic galls are found on the buds of various species of Quercus including the Pendunculate Oak (Quercus robur).

UK Status

Common throughout Britain.

VC55 Status

Common in Leicestershire and Rutland.

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Leicestershire & Rutland Map

MAP KEY:

Yellow squares = NBN records (all known data)
Coloured circles = NatureSpot records: 2020+ | 2015-2019 | pre-2015

UK Map