Neuroterus quercusbaccarum
| Neuroterus quercusbaccarum | |
|---|---|
 |
|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Hymenoptera |
| Family: | Cynipidae |
| Genus: | Neuroterus |
| Species: | N. quercusbaccarum |
| Binomial name | |
|
Neuroterus quercusbaccarum (Linnaeus, 1758) |
|
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 pedunculate oak (Quercus robur), or sessile oak (Quercus petraea) trees, caused by the cynipid waspNeuroterus quercusbaccarum which has both agamic and bisexual generations.
Previous names or synonyms for this species are Neuroterus baccarum, N. lenticularis, N. malpighii, Cynips lenticularis, C. quercus-baccarum, Spathegaster baccarum, S. varius, S. interruptor.
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.
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.
...
Wikipedia