Neuroterus gillettei

Neuroterus vernus var. exiguus

Cynipidae

Neuroterus

Quercus stellata

Alabama

Arkansas

Connecticut

Delaware

Florida

Georgia

Illinois

Indiana

Iowa

Kansas

Kentucky

Louisiana

Maryland

Massachusetts

Mississippi

Missouri

New Jersey

New York

North Carolina

Ohio

Oklahoma

Pennsylvania

Rhode Island

South Carolina

Tennessee

Texas

Virginia

West Virginia

Cynipid galls of the eastern United States

The Gall Wasp Genus Neuroterus

Neuroterus exiguus (sexgen)

Neuroterus exiguus n. sp.

After the discovery of a species of Neuroterus in my boxes of Andricus exiguus, I made at least three trips to West Rock to discover the home of the new species, sure that the galls of the two were not identical. The study of an unlimited amount of material revealed aments that were of abnormal size, some of them two or three times the ordinary diameter, some with nodular enlargements, but all more or less hidden in the florets. After repeated efforts I finally found some of the Neuroteri in these galls and the mystery was solved. These galls are so small and succulent that they soon shrivel up and disappear. When once found it was easy to discover them in considerable numbers, but even now I fail to detect them among bunches of dry Andricus galls.

New Species of North American Cynipidae (1900)

Neuroterus vernus variety exiguus bisexual form

Neuroterus gillettei

GALL. — As described for the species; swelling on petioles, mid- veins, or ament stems, or anther capsules on Quercus stellata (figs. 24, 25). 

RANGE. — Connecticut: Waterbury (?), West Rock (Bassett). New York (Beutenmuller). New Jersey: Lakehurst (Beutenmuller). Vir- ginia: Rosslyn. Probably confined to a northeastern area of the United States. 

Bassett found his galls in May, the insects emerging by the end of the month. My material from Rosslyn, Virginia, was about ready to emerge on May 16, 1920. 

Felt’s reference to N. floccosus on ament flowers is explained, by Dr. Felt himself, as a clerical confusion of exiguus with exiguissimus and the reduction of exiguissimus to a synonym of floccosus (following Beutenmuller) ; the reference applies to exiguus. 

Gillettei is certainly a complete synonym of exiguus. I have examined good series of paratypes of both names, com- paring them with types of all the related things, and cannot find any differences at all. The hosts of the two are the same. The two type localities are probably near together, altho the locality of gillettei was not definitely given, but in all such cases Bassett appears to have implied Waterbury, Connecticut, and the identity of the types of the two show they came from the same faunal area. The galls of the two names are different, exiguus coming from ament stem swellings (and anther cells), and gillettei from leaf petiole and midvein swellings, and these differences apparently prevented Bassett from seeing the relationship. The two descriptions were published on the same page, but were certainly written at different times, as evidence the great differences in the ordering of material, the choices of terms, etc. The differences in the galls, as for several related species of N euroterus, imply nothing more than that the insects are primitive, can produce only indefinite proliferations, do not restrict their activities to a single part of the host, and consequently are found in galls which vary as different tissues are affected. 

This is further apparent from an experience of mine which closely matches Bassett’s original experience with this insect. He obtained his Netiroterus exiguus types from boxes of galls which gave his Plagiotrichus exiguus (described as an Andricus) . He believed that this latter insect came from tiny, egg- shaped capsules in the aments, and at first he explained the shortened, thickened, compacted condition of the whole ament to the action of the Plagiotrichus. When he found the N eu- roterus in the box he cut open both anther capsule galls and the anther stem swelling. Concerning the anther capsule he states 'T examined the galls very carefully, but found but a single species, and from this the Andricus [Plagiotrichus] surely came, as I found a specimen in the unopened galls.” And later, concerning the stem swelling, he records "After repeated efforts I finally found some of the Neuroteri in these galls and the mystery was solved.” Solved, in part! 

I have large series of both insects from similarly combined clusters of anther capsules and ament stem swellings. My material is from Rosslyn, Virginia, on Q. stellata; I have compared both insects with types and cannot find differences, altho I am not convinced that Rosslyn, Virginia, and Water- bury, Connecticut, are in the same faunal area. At any rate, my material is specifically related to if not varietally identical with the Bassett types. I cut open anther and stem galls to determine the source of each insect. I found, in several instances for each species, both the Plagiotrichus and Neuroterus in both kinds of galls! Here is a case of gall dimorphism to match the several others in the genus, where the gall-producing capacity of the primitive N euroterus is not sufficient to obscure the nature of the plant tissue involved, and where the form of the gall thus varies as different plant tissues are attacked. But in this instance the interpretation is remarkably substantiated when we find two insects of distinct, but in both cases primitive genera, producing quite identical galls when the same part of the plant is attacked. It is possible that no other part of the plant but the ament and particularly the anther would restrict the gall as closely to form. The egg-shaped anther gall is now known from a number of species of Cynipidae of diverse genera (see the discussion of gall polymorphism in the introduction), and there seems to be little chance of the anther ever producing any other type of gall. This comparative, taxonomic study of species is giving us considerable information as to the factors which influence gall production. 

Neuroterus exiguus

Spindle-shaped fleshy enlargements of the staminate flower axis of Quercus stellata at Alexandria, Va., gave adults of this Neuroterus on May 12, 1920. The galls were also seen at Rosslyn. Along with these swellings and sometimes on them were tan-colored, thin-walled, somewhat hairy, oval galls evidently representing enlarged filaments which also seem to contain this Neuroterus. 

Field notes on gall-inhabiting cynipid wasps with descriptions of new species

Neuroterus exiguus

Quercus stellata
Flower galls
Fusiform enlargement of staminate axis, green, succulent, many-celled.

[Photo caption]
Q stellata. A fusiform enlargement of staminate axis. Adults emerged May 16, May 28-June 6; May 10-13 (DC).