Spongy Oak Apple Gall Wasp
( Amphibolips confluenta )


2012-0421-01100112-HYM02311-Amphibolips_confluenta[0943h33s,F,G,gall-tree-oak]{JRyugo}-G.jpg

PHOTO COMMENT

IDENTIFICATION
Identification:Amphibolips confluenta
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Common Name:Spongy Oak Apple Gall Wasp
Life Stage:(G) gall

PHYLOGENY

Phylum:Arthropoda
Class:Insecta
Superorder:Holometabola
Order:Hymenoptera
Family:Cynipidae
Tribe:Cynipini
Genus:Amphibolips
Taxon Code:HYM02311

LOCATION DETAILS
Location Name
Gardens at Lake Merritt, Lakeside Park, 666 Bellevue, Oakland
County:Alameda County
ECI Site#:CA01100110

RECOGNITION
Description
Oak Apple Gall Wasps are usually identified by their gall. Galls: This is a relatively very large (12-50 mm in diameter) gall which is about golf-ball sized. The inside has fibrous matter that radiates outward from the center of the gall. Galls formed during spring are green, but become light brown on drying with a thin, papery shell. Insect: Adults are small and dark cynipid wasps with oval, compressed abdomen. Larvae are small and globe-shaped.

BIOLOGY
Host
They occur principally on red, black, and scarlet oaks and form large, globose, thick-walled, hard, mottled, brownish or reddish galls on the side of the acorn cup, easily detached and dropping to the ground in the fall. Pink when fresh, becoming yellow and then blood-red, diameter 1/2 to 1 inch, on black, red, scarlet, Spanish and scrub oaks, August and September, shrivels, and becomes very hard. Also on pin, shingle, southern red, and water oaks.
Importance
This is one of many leaf galls that affect oaks. These galls usually damage the tree less than do twig galls. However, heavy infestations of this and other leaf galls can cause premature leaf fall and are unsightly on ornamental trees
Development
Galls, usually initiated during spring when young leaves are forming; sometimes they take over the entire leaf. Each contains a single larva inside a hard center capsule. The galls are produced on the midrib or stem of leaves.

CREDITS
Photographer
Jim Ryugo
Park Maintenance, City of Oakland

References
Species Amphibolips confluenta - Spongy Oak Apple Gall Wasp. (http://bugguide.net/node/view/39774). Accessed March 12, 2016. .
Russo, Ron. Field Guide to Plant Galls of California and Other Western States. California Natural History Guides. University of California Press. 2006.
Oak-Apple Gall Amphibolips confluenta. USDA Forest Service. (http://www.fs.fed.us/r8/foresthealth/pubs/oakpests/p34.html)


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