|Fruit or gall?|
Cutting it in half exposed either the single seed of a fruit (drupe) or a larva in a gall. The color was distinctive, but of what? Sad to say, Jay Barber called it a gall and nailed me with it. My only defense is that I was half right - it is an acorn plum gall from an oak tree. OK, he didn't buy "half right" either.
|Intact larva- MJ Hatfield|
The acorn plum gall is formed by a Cynipid wasp, Amphibolips quercusjuglans. As galls seldom do any significant damage to the parent tree, there is little research on many species. To quote backyardnature.net:
After Bugguide.net links, the trail grows cold. I hoped to find the derivation of the species name quercusjuglans, a strange mixture of quercus - Latin for oak, and juglans - genus name of walnuts. This is probably more than most people would care to know about the naming and sex life of this tiny wasp with the big nursery.
"We have over 750 species in 49 genera in the Gall Wasp Family. Furthermore, "Each species makes a characteristic gall on a specific part of the plant. Many make galls on oaks. Most have a complex life cycle with a parthenogenetic generation and a sexual one. Each generation makes galls of a different appearance and on different parts of the plant."
Gall wasp- MJ Hatfield