Biorhiza pallida
Oak apple gall wasp
Biorhiza pallida, Oak apple gall wasp. A small parasitic wasp with two alternating generations. A winged sexual generation develops within the familiar oak apples. Mating occurs and the female offspring migrate to the roots of the Oak to lay eggs. Eggs hatch into larvae that overwinter in small nodules on the roots. A new generation of wingless females move up the tree to lay eggs in buds. Upon hatching, the larvae cause the tree to form galls called oak apples. Found on English Oak, Quercus robur, and Sessile Oak, Quercus petraea.
Photograph detail
Slide 1: Biorhiza pallida, Oak apple gall wasp. Galls on young planted Oak tree, Quercus robur. West Wood, Redmire. May.
Slide 2: Biorhiza pallida, Oak apple gall wasp. Mature gall at the time of hatching on young planted Oak tree, Quercus robur. West Wood, Redmire. June.
Slide 3: Biorhiza pallida, Oak apple gall wasp. Section of a gall showing several larvae. Collected from a young planted Oak tree, Quercus robur. West Wood, Redmire. May.
Slide 4: Biorhiza pallida, Oak apple gall wasp. Section of a gall showing two larvae. Collected from a young planted Oak tree, Quercus robur. West Wood, Redmire. May.
Slide 5: Biorhiza pallida, Oak apple gall wasp. Winged sexual adult. Collected from a young planted Oak tree, Quercus robur. West Wood, Redmire. June.
Slide 6: Biorhiza pallida, Oak apple gall wasp. Winged sexual adult, side view. Collected from a young planted Oak tree, Quercus robur. West Wood, Redmire. June.