Andricus lignicola

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Cola-nut gall
Andricus lignicola - Cola-nut Gall.JPG
Mature galls on pedunculate oak
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Cynipidae
Genus: Andricus
Species: A. lignicola
Binomial name
Andricus lignicola
(Hartig, 1840)

Cola-nut galls[1] develop as a chemically induced distortion of leaf axillary or terminal buds on Pedunculate Oak (Quercus robur) or Sessile Oak (Quercus petraea) trees, caused by the agamic gall wasp Andricus lignicola (Hartig, 1840) which lays single eggs within leaf buds using their ovipositor. A previous name or synonym for the species A. lignicola is A. lignicolus and A. venheurni.

The physical appearance of the galls[edit]

Cola-nut gall cut open to show the unilocular cavity
Oak marble galls showing two stunted and two normal-sized examples

The galls are found in small groups, which however do not coalesce, helping to prevent mis-identification with the Oak marble gall (Andricus kollari), in addition the shape is ovoid rather than spherical and it is scaly rather than smooth. It grows up to about 10 x 8 mm and is at first green, rapidly changing to grey-brown, with light red patches where the original bud scales have separated. It is hard and firm, but does not always persist on the tree for very long.[2] Once the imago has emerged a small circular hole is apparent.[1]

Distribution[edit]

Cola-nut gall showing exit hole

It is well known in continental Europe, occurring from Holland to Asia Minor.

Life-cycle[edit]

The imago of the agamic phase emerges in early summer following the gall's inception. The bisexual generation gall is very similar to that of A. kollari, effecting the live bud of Quercus species[2] and has only been seen under culture conditions (1975).[3]

Predators, inquilines and parasitoids[edit]

Since its arrival in Britain Andricus quercuscalicis has acquired a guild of inquilines and parasitoids.[4][5]

Infestations of cola-nut galls[edit]

Removing and destroying cola-nut galls before they dry and the wasps emerge may help to reduce the infestation. While fairly large, and sometimes present in quite large numbers on scrub specimens, they cause no measurable harm.

See also[edit]

References[edit]

  1. ^ a b Darlington, Arnold (1975) The Pocket Encyclopaedia of Plant Galls in Colour. Pub. Blandford Press. Poole. ISBN 0-7137-0748-8. P. 155.
  2. ^ a b Stubbs, F. B. Edit. (1986) Provisional Keys to British Plant Galls. Pub. Brit Plant Gall Soc. ISBN 0-9511582-0-1. P. 52.
  3. ^ Darlington, Arnold (1975) The Pocket Encyclopaedia of Plant Galls in Colour. Pub. Blandford Press. Poole. ISBN 0-7137-0748-8. p. 155.
  4. ^ Hewett A E, Inhabitants of Knopper Galls in Hazelrigg Northumberland Cecidology 2006, Vol 21 (1) pp 9-21
  5. ^ Hails R S, Askew R R and Notton D G, The Parasitoids and Inquilines of the Agamic Generation of Andricus quercuscalicis (Cynipidae) In Britain, The Entomologist 1990, Vol 109 (3) pp 165-172.

External links[edit]

  • "Gall". Infoplease encyclopedia. Retrieved March 2006. 
  • "Andricus lignicola". Hedgerows, Hedges and Verges of Britain and Ireland (Hedgerowmobile). Retrieved December 2011.