Andricus kollari
| Andricus kollari | |
|---|---|
 |
|
| Female Andricus kollari of the asexual generation | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Hymenoptera |
| Family: | Cynipidae |
| Genus: | Andricus |
| Species: | A. kollari |
| Binomial name | |
|
Andricus kollari (Hartig, 1843) |
|
Andricus kollari is species of wasp which causes the formation of marble galls on oak trees.
Oak marble galls develop as a chemically induced distortion of leaf buds on pedunculate oak (Quercus robur), sessile oak (Quercus petraea) or their hybrid Quercus × rosacea, trees, caused by the parthenogeneticgall wasp (Andricus kollari, (Hartig, 1843)) which lays eggs within leaf buds using their ovipositor. The Turkey oak (Quercus cerris), introduced into Britain in 1735, is required for the completion of the life cycle of the gall. The oak marble gall is frequently confused with the oak apple gall, caused by another gall wasp, Biorhiza pallida. Oak marble galls are also known as the bullet gall, oak nut or Devonshire gall. Synonyms for the species are Cynips kollari, Andricus quercusgemmae, A. minor, A. indigenus and A. circulans.
The gall growth first appears as a rounded mass of green plant tissue on the leaf buds of the oak, later becoming hard and brown, being up to approximately 25 mm / 1 inch in diameter. Although nearly spherical, the galls often have a number of little flattened nodules. The rounded growths are filled with a spongy mass and a single wasp larva is located in a hard seed-like cell in the centre. The word 'marble' derives from the gall's shape, which is a marble-like rounded structure. As stated, although normally distinctive the oak marble gall can, under some growth conditions, be mistaken for the oak apple gall, caused by a number of gall wasps, such as Biorhiza pallida. This may be due to the observer's unfamiliarity with the true oak apple gall which grows to be somewhat larger, has red markings, but does grow on the axillary or terminal buds. The galls sometimes coalesce. The non-parasitised specimens are at the largest end of the size range.
Fused and/or stunted specimens can be confused with Andricus lignicola (Hartig), the 'Cola-nut gall'.
Originally these wasps were introduced to Devon from the Middle East in the 1830s.
The marble gall has alternating sexual and asexual generations, often taking two years to complete, especially in the north of Britain. The familiar summer gall develops from eggs laid by a sexual female in the developing buds of the two native oaks in May or June; the host trees often being immature or retarded, scrub-oak, specimens; they are rarer on older healthy trees.
...
Wikipedia