Clustered midrib gall on Post Oak

I have been wondering (for four long years) about the ID of a particular gall which has come to be known as the Clustered Midrib Gall. After some amazing collaboration between @megachile, @mileszhang, and myself we have finally solved the mystery!

There is quite a history to this gall, so this post is to record the abbreviated details for future reference.


The gall was first described by itself (without the larva or adult fly) from a Post Oak in 1862 by Osten Sacken. (Osten Sacken, 1862)

In 1887 Ashmead described a new wingless fly and erroneously thought the gall is the one Osten Sacken had described. He published that as Acraspis vaccinii (which later becomes Zopheroteras vaccinii), using Osten Sacken's description of the gall. (Ashmead, 1887)

In 1913 Beutenmuller described a new winged fly without the gall as Andricus lustrans. (Beutenmuller, 1913)

In 1918 Beutenmuller described a new winged fly and gall, which he named Andricus impositus, and even commented that he first thought it was Z. vaccinii but the fly did not match even though the gall did. (Beutenmueller, 1918)

In 1927, Weld figured out that the winged A. impositus fly is the same as the winged A. lustrans fly and described Callirhytis lustrans, the winged fly and the correct gall. In addition, he commented on 1) Ashmead's error, 2) the A. lustrans and A. impositus flies being the same species, as well as 3) Kinsey's Andricus dimorphus var. verifactor fly. (Weld, 1927)

Today, the current accepted name is Callirhytis vaccinii (Ashmead). (Krombein, 1979)

Zopheroterus vaccinii is the accepted name for the unrelated wingless fly and the correct gall it came from.

Weld points out that he found the same looking gall on Quercus breviloba in Austin and Boerne, Tex. Kinsey also reports the galls on Q. breviloba in Leander and Austin, Tex.


Weld's 1927 description of the Callirhytis lustrans gall is the most recent and accurate, and is transcribed here:

Callirhytis lustrans (BEUTENMUELLER)

Synonyms:
Andricus lustrans BEUTENMUELLER, Trans. Amer. Ent. Soc. vol. 39, 1913. p. 244.
Andricus impositus BEUTENMUELLER, Ent. News, vol. 29, 1918, p. 329.
Andricus dimorphus verifactor KINSEY, Indiana Univ. Studies 53, 1922, p. 15.
Acraspis vaccinii (gall only), ASHMEAD, Trans. Amer. Ent. Soc., vol. 14, 1887, p. 136.

Lustrans was described from two adults captured at Austin, Texas, gall and host unknown. One of these specimens was given in 1921 to the writer, who recognized its close relation to impositus. Lustrans is described as without a median groove, but this specimen in certain positions shows a faint median line, while the groove in some of the many available parataypes of impositus is fully as faintly defined. The writer is unable to separate paratypes of verifactor from lustrans. The gall of this species was first described by Osten Sacken in 1862, but Ashmead was evidently in error in thinking he had reared it in 1887, associating the wingless fly he reared with the wrong gall. These galls occur as midrib clusters on under side of leaves of Quercus stellata in the fall, dropping when mature. When fresh the individual galls are shaped like huckleberry flowers, somewhat cylindrical with the end distinctly truncate and depressed, but during the winter on the ground they become globular except for a short pedicel, and the depressed end becomes a flattened circular scar at apex with a slightly raised rim, and the greenish or reddish color changes to brown.

Beutenmueller sent the writer galls from New York City which contained pupae on November 1 and adults on November 25 (age of galls unknown). The writer collected galls at Poplar Bluff and Ironton, Mo.; Wharton, Trinity, Arlington, and Boerne, Tex.; Hugo, Okla. At Hugo they were just starting to develop on July 25. Galls collected in October, 1917, at Trinity, Tex., gave two adults May 18, 1919. In galls collected at Ironton in fall of 1917 pupae were found in October, 1918, and in March, 1919, flies emerging before May 12, 1919. S. A. Rohwer collected galls at Ironton in October, 1918, and reared adults April 9-16, 1919, and a few more were found dead in cage May 12, 1920 (Hopkins U. S. No. 10777j).

A precisely similar gall on the shin oak, Q. breviloba, was seen at Austin and Boerne, Tex., and may prove to be that of this species.


Illustration (Beutenmuller, 1909)


BIBLIOGRAPHY

Ashmead, William H., "On the Cynipidous Galls of Florida, with Descriptions of New Species and Synopses of the Described Species of North America" (1887)
URL: https://www.jstor.org/stable/25076487

Beutenmuller, William, "The Species of Biorhiza, Philonix and Allied Genera, and Their Galls" (1909)
URL: https://books.google.com/books?id=80RKAAAAYAAJ&pg=PA255

Beutenmuller, William, "Descriptions of New Cynipidae" (1913)
URL: https://www.jstor.org/stable/25076912

Beutenmuller, William, "Notes on Cynipidae, with Descriptions of a New Species (Hym.)" (1918)
URL: https://www.biodiversitylibrary.org/page/2570776#page/411

Kinsey, Alfred C., "Studies of Some New and Described Cynipidae (Hymenoptera)" (1922)
URL: https://www.biodiversitylibrary.org/page/7610739#page/363

Krombein, Karl V., "Catalog of Hymenoptera in America North of Mexico" (1979)
URL: https://archive.org/details/catalogofhymenop01krom/page/1106

Osten Sacken, Baron R., "Additions and Corrections to the paper entitled: 'On the Cynipidae of the North American Oaks and their Galls'” (1862)
URL: https://www.biodiversitylibrary.org/item/22852#page/297

Weld, Lewis H., "Field Notes on Gall-inhabiting Cynipid Wasps with Descriptions of New Species" (1927)
URL: https://www.biodiversitylibrary.org/page/7610739#page/363

Posted by kimberlietx kimberlietx, May 29, 2020 05:57

Comments

Awesome job laying this all out!

Posted by kitty12 about 2 years ago (Flag)

Fabulous research! I love it!

Posted by gcwarbler almost 2 years ago (Flag)

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