Neurotus quercus-baccarum on:
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The common spangle gall on the underside of leaves and the currant gall on the male catkins or occasionally the leaves, develop as chemically induced distortions on
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. 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 up 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.
Several different spangle type galls are found on oak leaves so close inspection is required for proper identification.
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.
The spangle galls are sometimes misidentified as scale insects.
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.
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.
Spangle galls
Google Images
Taxonomy
Spangle gall images
Video footage of Spangle Galls
{{Taxonbar, from=Q1905281 Cynipidae Gall-inducing insects Hymenoptera of Africa Hymenoptera of Asia Hymenoptera of Europe Wasps described in 1758 Oak galls Taxa named by Carl Linnaeus
pedunculate oak
''Quercus robur'', commonly known as common oak, pedunculate oak, European oak or English oak, is a species of flowering plant in the beech and oak family, Fagaceae. It is a large tree, native to most of Europe west of the Caucasus. It is widel ...
(''Quercus robur''), or sessile oak
''Quercus petraea'', commonly known as the sessile oak, Cornish oak, Irish Oak or durmast oak, is a species of oak tree native to most of Europe and into Anatolia and Iran. The sessile oak is the national tree of Ireland, and an unofficial embl ...
(''Quercus petraea'') trees, caused by the cynipid wasp ''Neuroterus quercusbaccarum'' which has both agamic and bisexual generations.
Previous names or synonyms for this species are ''Neuroterus
''Neuroterus'' is a genus of gall wasps that induce galls on oaks in which the wasp larvae live and feed. Some species produce galls that fall off the host plant and 'jump' along the ground due to the movement of the larvae within.
''Neuroteru ...
baccarum'', ''N. lenticularis'', ''N. malpighii'', ''Cynips lenticularis'', ''C. quercus-baccarum'', ''Spathegaster baccarum, S. varius'', ''S. interruptor''.
Galls
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. 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 up 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.
Several different spangle type galls are found on oak leaves so close inspection is required for proper identification.
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.
The spangle galls are sometimes misidentified as scale insects.
Distribution on the leaves
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.
Life cycle
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.Predators, inquilines, and parasitoids
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
''Torymus'' is a genus of chalcid wasps from the family Torymidae
Torymidae is a family of wasps in the superfamily Chalcidoidea. Most species in this family are small with attractive metallic coloration, and females generally have long ovipo ...
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.
Infestations
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.
Distribution
''N. quercusbaccarum'' is found throughout Europe, Asia Minor and North Africa.See also
*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 ...
* Oak artichoke gall
Andricus foecundatrix (formerly ''Andricus fecundator'') is a parthenogenetic gall wasp which lays a single egg within a leaf bud, using its ovipositor, to produce a gall known as an oak artichoke gall, oak hop gall, larch-cone gall or hop stro ...
* Rose bedeguar gall
''Diplolepis rosae'' is a gall wasp which causes a gall known as the rose bedeguar gall, Robin's pincushion, mossy rose gall, or simply moss gall.Darlington, Arnold (1975) ''The Pocket Encyclopaedia of Plant Galls in Colour.'' Pub. Blandford Pres ...
* ''Neuroterus albipes
''Neuroterus albipes'' is a gall wasp that forms chemically induced leaf galls on oak trees which has both bisexual and agamic generations and therefore forms two distinct galls, the smooth spangle gall and Schenck's gall.Darlington, Page 162 ' ...
''
* ''Neuroterus anthracinus
''Neuroterus anthracinus'' is a widely distributed gall wasp that forms chemically induced leaf galls on oak trees. ''N. anthracinus'' has both sexual and agamic generations and in consequence forms two distinct galls, the oyster gall and April ...
''
References
External links
Spangle galls
Google Images
Taxonomy
Spangle gall images
Video footage of Spangle Galls
{{Taxonbar, from=Q1905281 Cynipidae Gall-inducing insects Hymenoptera of Africa Hymenoptera of Asia Hymenoptera of Europe Wasps described in 1758 Oak galls Taxa named by Carl Linnaeus