Neuroterus quercusbaccarum

The spangle gall generation on the underside of the oak leaves are flat discs, with a distinct central elevation, slightly hairy, yellow-green at first and reddish later, attached by a short stalk. These galls are up to 6 mm in diameter, unilocular, unilarval with a whitish or yellow undersurface; they mature in September, detach and fall to the ground before the leaves themselves.{{cite journal |author=R. R. Askew |year=1962 |title=The distribution of galls of Neuroterus (Hym: Cynipidae) on oak |journal=Journal of Animal Ecology |volume=31 |issue=e3 |pages=439–455 |doi=10.2307/2045 |jstor=2045|bibcode=1962JAnEc..31..439A }} The larva continue to develop in the fallen spangle and, protected by the leaf layer, they overwinter. Any spangle galls that remain attached to the leaves dry and die.

The smooth surfaced currant gall generation appears in April and lay unfertilised eggs in the staminate catkins or occasionally the developing young leaves. The resulting spherical galls are around 4 mm in diameter, unilocular and unilarval, green at first, maturing through pink to red, therefore closely resembling redcurrants.{{cite book |last=Stubbs |first=F. B. |year=1986 |title=Provisional Keys to British Plant Galls |publisher=British Plant Gall Society |isbn=0-9511582-0-1 |page=48}}

Several different spangle type galls are found on oak leaves so close inspection is required for proper identification.{{cite web |url=http://www.bugsandweeds.co.uk/galls%20p1.html |title=Oak Common Spangle gall |publisher=A Nature Observer's Scrapbook |accessdate=August 15, 2009 |archive-date=September 23, 2010 |archive-url=https://web.archive.org/web/20100923181701/http://bugsandweeds.co.uk/galls%20p1.html |url-status=dead }}

The suckers at the base of older trees are often more heavily infested than the mature tree foliage. This may be due to the poor flying abilities of N. quercusbaccarum or it may relate to the physiological age of the leaves.{{cite journal |author=J. S. Hough |year=1953 |title=Studies on the common spangle gall of oak. III. The importance of the stage in laminar extension of the host leaf |journal=New Phytologist |volume=52 |issue=3 |pages=229–237 |jstor=2429572 |doi=10.1111/j.1469-8137.1953.tb07513.x|doi-access=free }}

The spangle galls are sometimes misidentified as scale insects.{{cite web |url=http://www.rhs.org.uk/advice/profiles0900/oak_galls.asp |title=Oak galls |publisher=Royal Horticultural Society |accessdate=August 15, 2009 |url-status=dead |archiveurl=https://web.archive.org/web/20090715180010/http://www.rhs.org.uk/advice/profiles0900/oak_galls.asp |archivedate=July 15, 2009 }}

The distribution and numbers of spangle galls on mature oak trees differs from that on young trees; the differences could be partly due to the earlier date of leaf opening on mature trees. No spatial zonation of spangle galls was apparent on the mature trees. Galls on catkins are less parasitised than those on leaves.{{cite journal |author=Olivier Plantard & Michael E. Hochberg |year=1998 |title=Factors affecting parasitism in the oak-galler Neuroterus quercusbaccarum (Hymenoptera: Cynipidae) |journal=Oikos |volume=81 |issue=2 |pages=289–298 |doi=10.2307/3547049 |jstor=3547049|bibcode=1998Oikos..81..289P }}

The male and female of the bisexual generation emerge in June from the currant galls and after mating the fertilised eggs are laid in the lower epidermis of the oak leaves. The spangle galls develop over the winter and the insects emerge in April, laying their eggs in the catkins or lower epidermis. The cycle, an alternation of generation, then begins again.

File:Common Spangle gall.JPG|left|upright|Common spangle galls on a Quercus robur leaf

File:Common Spangle Gall - leaf upper.JPG|Upper surface of galled leaf

File:Currant Gall Neuroterus quercusbaccarum on Sessile Oak Quercus petraea (27881771009).jpg|Sexual generation gall

File:Eikennapjesgal Neuroterus albipes forma laeviusculus-levelsadjust-mask.jpg|The gall wasp N. albipes, similar to N. quercusbaccarum

File:2021 07 27 Torymus auratus 1b.jpg| Parasitoid Torymus auratus

Spangles lying on the ground are often eaten by gamebirds and both of these galls are prone to being colonised by a variety of other organisms. Synergus spp. are inquilines which attack small galls, and the primary parasitoid Mesopolobus tibialis attacks medium size galls and Torymus auratus attacks large galls. The two parasitoids affect the final mature size of the spangle galls, highlighting the galling insects chemical influence upon the host plant.{{cite journal |author=Oliver Plantard, Jean-Yves Rasplus & Michael E. Hochberg |year=1997 |title=Resource partitioning in the parasitoid assemblage of the oak galler Neuroterus quercusbaccarum L. (Hymenoptera: Cynipidae) |volume=17 |issue=1 |pages=1–15 |url=http://mike.hochberg.free.fr/MEHAO96Plant.pdf }}

From 80 to 100 spangle galls can develop on the underside of each leaf and therefore vast numbers fall onto the ground in September, sometimes completely colouring and covering the ground. Infestations do not have any serious effect upon galled trees.

N. quercusbaccarum is found throughout Europe, Asia Minor and North Africa.{{cite web |url=http://www.probertencyclopaedia.com/cgi-bin/res.pl?keyword=Common+Spangle+Gall+Wasp&offset=0 |title=Common Spangle Gall Wasp |publisher=Probert Encyclopedia |accessdate=August 15, 2009 |url-status=dead |archiveurl=https://web.archive.org/web/20080618230307/http://www.probertencyclopaedia.com/cgi-bin/res.pl?keyword=Common+Spangle+Gall+Wasp&offset=0 |archivedate=June 18, 2008 }}

{{Div col}}

• Knopper gall
• Oak artichoke gall
• Rose bedeguar gall
• Neuroterus albipes
• Neuroterus anthracinus

{{Div col end}}

{{Reflist|30em}}

• [http://www.boxvalley.co.uk/nature/sns/wad58/w58-09.html Spangle galls]
• [http://www.gwydir.demon.co.uk/insects/cynipidae.htm Cynipids]
• [http://images.google.co.uk/images?client=firefox-a&rls=org.mozilla:en-GB:official&channel=s&hl=en&q=Neuroterus+quercusbaccarum&um=1&ie=UTF-8&ei=mXR-SqKtIYXSjAetr_TvAQ&sa=X&oi=image_result_group&ct=title&resnum=4 Google Images]
• [http://zipcodezoo.com/Animals/N/Neuroterus_quercusbaccarum/ Taxonomy]
• [http://tt.ibt.lt/v/insecta/hymenoptera/cynipidae/Neuroterus_quercusbaccarum/ Spangle gall images]
• [http://www.micropics.org.uk/Cynipidae/neuroterus/quercusbaccarum/neuroterus%20quercusbaccarum.htm The gall insect]
• [https://www.youtube.com/watch?v=K8JvbIWXsP8 Video footage of Spangle Galls]

{{Taxonbar|from=Q1905281}}

Category:Cynipidae

Category:Gall-inducing insects

Category:Hymenoptera of Africa

Category:Hymenoptera of Asia

Category:Hymenoptera of Europe

Category:Oak galls

Category:Taxa named by Carl Linnaeus

Category:Wasps described in 1758