Xystoteras contorta

Cynipidae

Neuroterus

Quercus sinuata breviloba

Alabama

Arkansas

Florida

Georgia

Louisiana

Mississippi

Oklahoma

South Carolina

Texas

Quercus stellata

Connecticut

Delaware

Illinois

Indiana

Iowa

Kansas

Kentucky

Maryland

Massachusetts

Missouri

New Jersey

New York

North Carolina

Ohio

Pennsylvania

Rhode Island

Tennessee

Virginia

West Virginia

American gallflies of the family Cynipidae producing subterranean galls on oak

The Gall Wasp Genus Neuroterus

Neuroterus contortus (agamic)

Xystoteras contorta, new species. Agamic

Host.--Quercus breviloba, Quercus stellata

Gall.--Gnarled woody swellings at base of young sprouts which are only a few millimeters in diameter. Covered with normal bark. Polythalamous.

Type locality.--Austin, TX. Collected galls on Q breviloba October 30, 1917, both old galls and fresh ones with pupae in. Living adults were cut out on December 12. Collected one gall on Q. stellata at Palestine, Texas, October 16, 1917, and cut out one fly December 1. 

Neuroterus contortus 

GALL. — An irregular stem swelling, wholly inseparable. Polythalamous. Individual galls up to 20. mm. long and 8. mm. wide, but sometimes several galls are closely adjacent and more or less fused. Externally very rough, small, irregular, raised spots indicating some of the larval cells; covered with greenish, young bark, drying browner. Internally woody, most woody centrally, with a great many, densely packed, small larval cells, 1.7 mm. long by 0.7 mm. in width, mostly toward the surface; the lining distinct but wholly inseparable. On young stems, involving young petioles and deforming the young leaves; at the crowns (or on roots?) of Quercus breviloba (figs. 58, 59). 

RANGE. — Texas: Austin. Probably occurs thruout eastern Texas and adjacent parts of Louisiana and Oklahoma. The agamic generation is known from galls and adults obtained by Weld in 1917, and from a quantity of material Dr. J. T. Patterson has bred. Several hundred insects of the bisexual generation were bred by Dr. Patterson in the spring of 1922. I first connected the alternate generations of this insect on the basis of the complementary dates of development and the extremely close similarity of the insects and galls, and this similarity is enough to make the relation unquestionable. Dr. Patterson confirms this by his experimental data. 

The agamic generation starts growth in April; Dr. Patterson describes the galls as nearly fully formed by the last of April, with small larvae in the galls by July; Weld found pupae on October 16 and 30, with live adults in the galls on December 1 and 12. Emergence is in the relatively mild winter season of Texas or in the early spring, from before the last of January to after the 7th of February, according to Dr. Patterson’s records. Dr. Patterson states that he has secured 10 males with 231 females of this agamic generation, but that these males are unable to mate with the females, altho they attempt to copulate; the females appear to have completely lost the mating instincts, as have the males to some degree. These males are apparently functionless, which is a most interesting case of this sex persisting as a generation becomes agamic. I have seen four of these males. The bisexual generation develops quickly in the spring. Dr. Patterson obtaining adults on April 3, 1922. He has sent me almost three times as many males as females, so probably the sexes occur in about equal numbers. The galls of the two generations are similarly located at the crown of the tree, and differ very little in structure. I do not see any differences between the insects of the two except in the larger size which is almost always correlated with agamic reproduction of Cynipidae. The close similarity of the alternates is one reason for placing contortus in this genus. This is the only root gall yet known in Neuroterus, but the gall is sometimes on stems at the crown of the tree. Weld records a specimen of this species obtained from Palestine, Texas, on Quercus stellata. It may belong to a distinct host variety. Probably still other white oaks of eastern Texas, Louisiana, and Oklahoma are hosts for this species. 

Neuroterus contortus agamic form contortus 

GALL. — Not greatly different from the gall of the other generation, somewhat larger and more smooth, probably due to the leaves having worn off (fig. 59).

Neuroterus contortus agamic

Quercus breviloba, stellata
"Root" galls
Gnarled woody swellings at base of small young sprouts in October, then containing pupae.

[Photo caption]
On Quercus breviloba. Also on Q stellata. Galls contained pupae on Oct 30 and adults were cut out Dec 12 (TX). The similar gall of the sexual generation is said to develop quickly in the spring, adults emerging Apr 3.

Cynipid galls of the eastern United States