Neuroterus fragilis
(sexgen)sexgen:The sexual generation (AKA bisexual generation or sexgen) of an oak gall wasp (cynipini) species consists of both male and female wasps, which mate before the females lay eggs which will mature to form the all-female agamic generation.
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The gall's range is computed from the range of all hosts that the gall occurs on. In some cases we have evidence that the gall does not occur across the full range of the hosts and we will remove these places from the range. For undescribed species we will show the expected range based on hosts plus where the galls have been observed.
Our ID Notes may contain important tips necessary for distinguishing this gall
from similar galls and/or important information about the taxonomic status of
this gall inducer.
Created Feb 4, 2026 1:47 PM UTC
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Last updated Feb 4, 2026 1:47 PM UTC
The Gall Wasp Genus Neuroterus
Alfred Kinsey
(1923)
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.
