Cynips quercusfolii
Cherry gall
Cherry galls are not plants or fruits. They are homes built by trees at the direction of a wasp, specifically by Cynips quercusfolii, a gall wasp. They are found on Quercus frainetto, Q. macranthera, Q. petraea, Q. pubescens, Q. pyrenaica, Q. robur, and rarely, Q. cerris.
Identification: Cherry galls are created when a gall wasp larva secretes substances on some oak species, commandeering the plant’s cellular machinery into building a “house.” The house acts as an incubation chamber, food source, and complete miniature habitat for the larva. How cool is that? Galls are ½–⅞″ (1.5–2.5 cm) in diameter, yellow-green with pink or bright red, sometimes smooth and shiny, sometimes warty. The wasps themselves are less than ¼″ (6.3 mm) long and black, and the larva occupies a tiny hollow in the middle of the gall. Galls form from July to October, maturing in August.
Online References:
Www.biolib.cz (wasp and gall photos)
Wikimedia Commons (photos)
Www.dreamstime.com (more photos)
References:
Redfern, Margaret, Plant Galls, Collins, 2011, p. 267, 334, 341-2, 474, 489-90
9/16/2017 · Wills Hole/Town Forest, Acton, Massachusetts · ≈ 1¾ × 1½″ (4.5 × 4.3 cm) 
On sessile oak (Quercus petraea) · 7/31/2012 · Bemis Rd Conservation Area, Pepperell, Massachusetts · ≈ 3½ × 5″ (9.2 × 13 cm) 
ID is uncertain 
9/16/2017 · Wills Hole/Town Forest, Acton, Massachusetts · ≈ 1¾ × 1¾″ (4.9 × 5 cm) 
9/23/2007 · Near Mike & Ellen’s, Milford, Pennsylvania 
On sessile oak (Quercus petraea) · 7/31/2012 · Bemis Rd Conservation Area, Pepperell, Massachusetts · ≈ 5 × 3½″ (13 × 9.2 cm) 
9/5/2009 · Orange Trail, Willard Brook State Park, Townsend, Massachusetts · ≈ 3 × 2″ (7.8 × 5.2 cm) 
8/28/2017 · Lowell-Dracut-Tyngsboro State Forest, Lowell, Massachusetts · ≈ 1¾ × 1¾″ (4.8 × 4.7 cm) 
On sessile oak (Quercus petraea) · 7/31/2012 · Bemis Rd Conservation Area, Pepperell, Massachusetts · ≈ 5 × 8″ (13 × 19 cm) 
On sessile oak (Quercus petraea) · 7/31/2012 · Bemis Rd Conservation Area, Pepperell, Massachusetts · ≈ 3½ × 2½″ (9 × 6.8 cm) 
9/23/2007 · Near Mike & Ellen’s, Milford, Pennsylvania 
| Parents | Unknown | Genus is not in the current taxonomy |
| Genus | Cynips | Oak gall wasps. From New Latin, altered from Late Latin cyniphes, “a kind of stinging insect,” corrupt form of Ancient Greek κνίψ (kníps), varying with σκνίψ (skníps) |
| Species | quercusfolii | Oak leaf gall |
Cynips quercusfolii description by Thomas H. Kent, not updated.
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