Oh the Gall
While doing some yard clean up recently I gathered up some brown balls that had a sponge like center when I tore them open, the little paper-like spheres I later learned were actually brown oak apple galls, Amphibolips confluenta . These galls are easily seen now that the leaves are falling in the dense oak stands of South Eastern New England. 
The ping pong size balls were earlier in the season home base to a gall wasp and when I say earlier I read they likely left the gall prior to Memorial Day!
Each oak apple gall was home to one single wasp and these Paper Mache like balls are empty because their former residents literally flew the coop, which can only happen during a specific cycle in their life. Note that each gall has a tiny hole which is the wasps escape hatch. As I understand it gall wasps are similar to butterflies in the sense that they have life stages/cycles that don’t resemble each other which is a trait that is known as “alternation of generations”.
The brown galls that we see on the ground or still hanging on during the fall were likely formed in the spring when a wingless gall wasp injected her egg into the base or midrib of a newly forming leaf.
The egg causes the oak leaf to swell and create a green gall. I think it is important to understand that the gall is part of the tree/plant not part of the insect and that each gall is home to only one wasp.
When the Oak Apple Gall Wasp Amphibolips confluenta drills its way out of the gall, it has wings and is either a male or female that is now looking to mate. Afterwards I can only imagine that the males have headed off looking for more love, but of course the fertile female goes back to work and digs down into the soil below the oak tree where she lays her eggs into the oak trees roots.
This causes root galls to form which take about sixteen months to mature after which the wingless female emerges then climbing up the oak tree she lays her eggs in a leaf bud creating the Oak Apple Gall.
The ping pong size balls were earlier in the season home base to a gall wasp and when I say earlier I read they likely left the gall prior to Memorial Day!
Each oak apple gall was home to one single wasp and these Paper Mache like balls are empty because their former residents literally flew the coop, which can only happen during a specific cycle in their life. Note that each gall has a tiny hole which is the wasps escape hatch. As I understand it gall wasps are similar to butterflies in the sense that they have life stages/cycles that don’t resemble each other which is a trait that is known as “alternation of generations”.
The brown galls that we see on the ground or still hanging on during the fall were likely formed in the spring when a wingless gall wasp injected her egg into the base or midrib of a newly forming leaf.
The egg causes the oak leaf to swell and create a green gall. I think it is important to understand that the gall is part of the tree/plant not part of the insect and that each gall is home to only one wasp.
When the Oak Apple Gall Wasp Amphibolips confluenta drills its way out of the gall, it has wings and is either a male or female that is now looking to mate. Afterwards I can only imagine that the males have headed off looking for more love, but of course the fertile female goes back to work and digs down into the soil below the oak tree where she lays her eggs into the oak trees roots.
This causes root galls to form which take about sixteen months to mature after which the wingless female emerges then climbing up the oak tree she lays her eggs in a leaf bud creating the Oak Apple Gall. Photos are courtesy of Thérèse Arcand.
