Neuroterus quercicola var. fragilis

Cynipidae

Neuroterus

Quercus berberidifolia

California

Quercus douglasii

Quercus dumosa

Quercus durata

Quercus lobata

Nevada

Quercus pacifica

Cynipid Galls of the Pacific Slope

Neuroterus fragilis (sexgen)

Neuroterus fragilis

Host: Quercus virens (?) [sic]

Gall spherical, hemispherical or conical, usually succulent, and consisting of a wall that encloses a chamber in which the larval cell lies free; some of these galls are loosely attached to the leaf, but more often they are imbedded in the blade.

An illustrated catalogue of American insect galls

Neuroterus quercicola variety fragilis

GALL. — Typical for the species, rather small, on the midveins, involving the blades; an irregular, polythalamous swelling up to 6 mm. in diameter; on Quercus dumosa. 

RANGE. — California: San Diego (vicinity) (Bassett) ; Pasadena, Upland. Probably thruout southern California from Palo Alto and El Portal south, wherever Q. dumosa occurs. 

I have not seen insects of this variety, and have depended upon the meager, original description for my note on the adult. I have galls from Pasadena and Upland which agree with the original description and with the figure given by Beutenmuller (1910). The Beutenmuller material, altho not definitely designated, would appear to have come from Bassett. The small galls with small exit holes would favor Beutenmuller’s 0.7 mm. instead of Bassett’s .05 inches for the length of the insect. My galls, as well as Beutenmuller’s, are from Q. dumosa; Bassett recorded the host as ‘'a small oak in southern California, probably Q. virens or a related species.” Wold, in McCracken and Egbert, considered fragilis and pacificus synonyms, and those authors, confusing the two in- sects, intimate that Q. Douglctsii and Q. lobata are the hosts of fragilis. Of course neither Douglasii nor lobata occur within nearly a hundred miles of the type locality of fragilis. Dumosa and Engelmannii are the only white oaks near San Diego, and since dumosa is the only small oak in accord with Bassett's description, this would appear to be the host of this variety. I have never seen the same variety of a cynipid on Q. lobata in Central California and on Q. dumosa in southern California, and there is hardly a chance that fragilis and pacificus are not distinct. 

The Gall Wasp Genus Neuroterus

Neuroterus fragilis Bass. 

Quercus douglasii, dumosa
Leaf galls, integral
Fig 118. Abrupt parenchyma thickening.

118. Q dumosa, durata, douglasii. Develop in early spring. Flies were emerging Mar. 51 (Santa Catalina Island); April 25 (Paso Robles); May 1 (Palo Alto). Had not emerged by May 10 at Ukiah.


Neuroterus fragilis

[Hosts: Quercus durata, berberidifolia, douglasii]

New galls are succulent and green as early as March but turn brown by midsummer. 

Plant Galls of the Western United States

Catkin galls were included based on the comment by Joyce Gross [here](https://www.inaturalist.org/observations/40959545)

Quercus lobata is included as a host based on Ron Russo's speculation on [this observation](https://bugguide.net/node/view/758229) on BugGuide; other observations ([eg](https://www.inaturalist.org/observations/80192884), [2](https://www.inaturalist.org/observations/40959544)) on this host support the assumption but the relationship has not been confirmed by adult morphology. 

Quercus pacifica is added as a host based on this observation in [April](https://www.inaturalist.org/observations/15023457).