''Andricus grossulariae'' is a gall wasp species inducing agamic acorn cup galls on oak tree acorn cups and sexual phase galls on catkins. Synonyms include ''Andricus fructuum'' (Trotter, 1899), ''Andricus gemellus'' (Belizin & Maisuradze, 1961), ''Andricus intermedius'' (Tavares, 1922), ''Andricus mayri'' (Wachtl, 1879) and ''Cynips panteli'' (Kieffer, 1897).

Galls

Acorn cup galls develop as a chemically induced distortion of the growing acorn cups on oak trees, caused by

gall wasp Gall wasps, also incorrectly called gallflies, are hymenopterans of the family Cynipidae in the wasp superfamily Cynipoidea. Their common name comes from the galls they induce on plants for larval development. About 1,300 species of this generall ...

s which lay eggs within the tissues of the acorn cup. The sexual phase appears on catkins as rounded structures (6 mm × 3–4 mm) possessing a characteristic point, and when young are covered with fine hairs. The galls, shiny and hard, turn red in colour and then black or dark purple. The asexual or

parthenogenetic Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and development ...

phase, about 10 mm across, develops on acorn cups of English oak ''Q. robur'' and sessile oak ''Q. petraea''. The galls, formed of flattened projections, often enclose the immature acorn. The galls first appear pink in colour and as they mature they turn red, then green and finally brown during their development. Previously the causer of this stage was known as ''Andricus mayri'' (Wachtl). Although normally distinctive the asexual acorn cup gall can, under some growth conditions, be mistaken for the

knopper gall ''Andricus quercuscalicis'' is a gall wasp species inducing knopper galls. Knopper galls develop as a chemically induced distortion of growing acorns on pedunculate oak (''Quercus robur'' L.) trees, caused by gall wasps, which lay eggs in buds w ...

, caused by the gall wasp ''

Andricus quercuscalicis ''Andricus quercuscalicis'' is a gall wasp species inducing knopper galls. Knopper galls develop as a chemically induced distortion of growing acorns on pedunculate oak (''Quercus robur'' L.) trees, caused by gall wasps, which lay eggs in buds w ...

''. ''A. grossulariae'', although usually found on acorns, is also found on buds.

Life cycle

As stated, two forms of galls exist for this species, the asexual phase inducing the acorn cup gall on the cups in late summer and the sexual phase inducing rounded galls on the oak catkins in spring.

Parasitoids and inquilines

One study identified twenty-four

parasitoid In evolutionary ecology, a parasitoid is an organism that lives in close association with its host (biology), host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionarily stable str ...

s from galls of ''A. grossulariae'', such as ''Torymus auratus'', ''Megastigmus dorsalis'', ''Ormyrus pomaceus'', '' Sycophila variegata'', ''Sycophila biguttata'', ''Mesopolobus xanthocerus'', and ''Aulogymnus trilineatus''. ''Ceroptres cerri'' is an inquiline of ''A. grossulariae''.

Distribution

''A. grossulariae'' has been recorded from the United Kingdom, Spain, Belgium, and Israel. ''A. grossulariae'' was first seen in Britain in

Berkshire Berkshire ( ; in the 17th century sometimes spelt phonetically as Barkeshire; abbreviated Berks.) is a historic county in South East England. One of the home counties, Berkshire was recognised by Queen Elizabeth II as the Royal County of Berk ...

in 2000.

References

External links