Quiz time again....

This is another plant gall - a chemically induced reaction by the host plant to the presence of a causal organism. This time caused by another species of wasp, like the oak marble gall wasp, called Neuroterus quercusbaccarum. The galls you see in the picture are known as oak spangle galls.

This species of wasp has two different generations per year (in a similar way to the oak marble gall wasp), having a sexual and a parthenogenetic (asexual) generation. The spangle galls are caused by a sexual female, who has mated with a male wasp and laid her eggs on the underside of an oak leaf. The eggs are laid during the flight period of May - July and the disc shaped spangle galls appear from July onwards, at first appearing green-yellow in colour and then darkening to red/brown with age. They are up to 5mm long, raised in the middle, slightly bristly and are attached to the leaf by a tiny stalk.

The galls then overwinter on the ground in amongst leaf litter, with the developing wasp larva still inside - one larva per gall. When fully developed, the imago (adult) insect emerges from the gall in January - May. This is the parthenogenetic generation and comprises female only wasps that do not require a male in order to reproduce. The wasp lays her eggs on the male catkins of oak trees in the spring and it is this generation that causes another type of gall known as the current gall. These galls look quite different to the spangle galls, being spherical, 4-7mm in diameter and can range in colour from green, to yellow, red or purple. They appear in May - June, with the sexual generation comprising males and females emerging from May - July. The wasps mate and the cycle starts over again.

The wasps themselves are tiny, only up to 3mm long with a slight variation in males and females and among generations. They are fairly common throughout the UK and affect both our native oak trees, the pedunculate oak, Quercus robur and the sessile oak, Quercus petraea.

This is another plant gall - a chemically induced reaction by the host plant to the presence of a causal organism. This time caused by another species of wasp, like the oak marble gall wasp, called Neuroterus quercusbaccarum. The galls you see in the picture are known as oak spangle galls.

This species of wasp has two different generations per year (in a similar way to the oak marble gall wasp), having a sexual and a parthenogenetic (asexual) generation. The spangle galls are caused by a sexual female, who has mated with a male wasp and laid her eggs on the underside of an oak leaf. The eggs are laid during the flight period of May - July and the disc shaped spangle galls appear from July onwards, at first appearing green-yellow in colour and then darkening to red/brown with age. They are up to 5mm long, raised in the middle, slightly bristly and are attached to the leaf by a tiny stalk.

The galls then overwinter on the ground in amongst leaf litter, with the developing wasp larva still inside - one larva per gall. When fully developed, the imago (adult) insect emerges from the gall in January - May. This is the parthenogenetic generation and comprises female only wasps that do not require a male in order to reproduce. The wasp lays her eggs on the male catkins of oak trees in the spring and it is this generation that causes another type of gall known as the current gall. These galls look quite different to the spangle galls, being spherical, 4-7mm in diameter and can range in colour from green, to yellow, red or purple. They appear in May - June, with the sexual generation comprising males and females emerging from May - July. The wasps mate and the cycle starts over again.

The wasps themselves are tiny, only up to 3mm long with a slight variation in males and females and among generations. They are fairly common throughout the UK and affect both our native oak trees, the pedunculate oak, Quercus robur and the sessile oak, Quercus petraea.