''Andricus aries'' is a species of gall-forming wasps, in the genus '' Andricus''. The species was named by the French

entomologist Entomology () is the scientific study of insects, a branch of zoology. In the past the term "insect" was less specific, and historically the definition of entomology would also include the study of animals in other arthropod groups, such as arach ...

Joseph-Étienne Giraud Joseph-Étienne Giraud (31 January 1808, Briançon – 28 May 1877, Paris) was a French doctor and entomologist specializing in Hymenoptera with an additional interest in Coleoptera. Giraud practised medicine in Vienna and Paris. He became the Pre ...

, in 1859. It is commonly found in eastern Europe and during the 21st century has spread to western Europe.

Description

Adults lay their eggs on various species of oak, including '' Quercus robur'', '' Q. petraea'', '' Q. pubescens'' and '' Q. cerris'', The developing larvae cause the trees to create an elongated

gall Galls (from the Latin , 'oak-apple') or ''cecidia'' (from the Greek , anything gushing out) are a kind of swelling growth on the external tissues of plants, fungi, or animals. Plant galls are abnormal outgrowths of plant tissues, similar to be ...

, reminiscent of a ram's horn, hence the epithet '' aries'' and the vernacular name "ram's horn gall wasp". Green at first, the gall can be reduced to a single strap or can just be 5 mm long. It later hardens, turns brown and is especially variable when the gall contains inquilines ('' Synergus'' species). ''A. aries'' does not cause galls to form on acorns but causes galls to develop on leaf buds on twigs, these have a variety of forms which are due to the activities of parasites and inquilines. Its sexual stage is found on the catkins of Evergreen Oak In northwestern Europe, at least, their reproduction is solely asexual generation, however, experiments have demonstrated that newly emerged females will lay eggs in the axillary buds of '' Quercus cerris''. ''A. aries'' has been found, like other species of gall wasp which have colonised the British Isles, to have been utilised by native

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 since their arrival, and that their parasitoids from continental Europe have not followed them across the English Channel.

Distribution

It is found primarily in eastern Europe, but in the 21st century has spread to western Europe including the United Kingdom. If was first recorded in Maidenhead Thicket, Berkshire in 1997 and since then has spread all over the southern half of England.

References

External links

Plant Parasites of Europe
Andricus aries - Sot's Hole - 2014-09-03 - Andy Mabbett - 04

{{Taxonbar, from=Q14678420 Cynipidae Gall-inducing insects Hymenoptera of Europe Insects described in 1859 Oak galls Taxa named by Joseph-Étienne Giraud