The dictionary widget in Apple OS X defines “gall” as …

gall 3 |gôl|
an abnormal growth formed on plants and trees, esp. oaks, in response to the presence of insect larvae, mites, or fungi.
• [ as modifier ] denoting insects or mites that produce such growths: gall flies.

The following photos show an unknown insect gall on Swamp Rose (Rosa palustris) spotted during a photowalk through the central wetland area at Huntley Meadows Park on 06 November 2013.

Unknown insect gall

Closer view.

Unknown insect gall

Wider view.

Charley Eiseman, widely regarded as the go-to gall guy, said “It is likely a Diplolepis sp. gall.” Diplolepis is a genus of gall wasp in the Family Cynipidae.

Thanks to Joshua Stuart Rose for providing a detailed answer to my questions, “What is the typical timeline for development of a gall like this one (including the life cycle of the insects living inside the gall), and what is the role of the “host” plant?”

Charley can correct me if I’m wrong, but the host plant is both protection and food for the gall inhabitant. The insect somehow incites growth of the gall, sometimes by bringing along a pathogenic fungus or virus, other times by releasing hormones or even segments of genetic material. The insect then eats what is growing in the gall’s interior. Meanwhile, the plant’s bark or skin, already adapted to protect the interior tissues of the plant, protects the insect right along with. The timeline is tough to figure without knowing the species, but if there’s anything overwintering in there, I would bet on its emerging from the gall in April or May. That’s assuming that it did not already emerge in the autumn to overwinter as an adult somewhere, or else emerged even further back in time so it could mate and overwinter as eggs, waiting to form their own galls after they hatch in the spring. Source Credit: Joshua Stuart Rose, member of the BugGuide group on Facebook.

Charley Eiseman added the following comment:

That all sounds right to me. I don’t see exit holes so I’m guessing there is still something inside. Also, it seems to be the case that stem swelling type galls overwinter. Source Credit: Charley Eiseman, member of the BugGuide group on Facebook.

Copyright © 2014 Walter Sanford. All rights reserved.

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One Response to “Gall”

  1. Parasitic gall wasps | walter sanford's photoblog Says:

    […] out the growth is a gall caused by a parasitic wasp. Charley Eiseman, widely regarded as the go-to gall guy, said “It is […]

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