Atrusca capronae

Quercus subturbinella [turbinella]
Leaf galls
Detachable
Fig 164.

Cynips (dugèsi) capronae (Weld)
agamic form
Figures 9, 18, 41, 56

Diplolepis capronae Weld, 1930, Proc. Ent. Soc. Wash. 32:29.
Diplolepis Capronae Houard, 1934, Marcellia 28:35, figs. 14, 15

GALL.-Similar to other galls of the dugèsi and bella complexes, sometimes somewhat flattened basally, but sometimes with the vertical longer than the horizontal axis; up to 18. mm., averaging nearer 10. mm. in diameter; surface smooth and shining; older galls light brownish yellow, conspicuously striped with vertical, rarely anastomosing bands of purplish brown. Figures 9, 56.

HOST.-Quercus subturbinella, a desert scrub of Californian affinities.

RANGE.-Arizona: Camp Creek (Weld coll., types). Globe. Safford (galls only). Utah : Zion Park (questionable determ.). Possibly restricted to Quercus sub turbinella in an area in Central Ari zona, north of a line drawn from Safford to Phoenix. Possibly it is the same species ranging on the same oak into Southwestern Utah. Figure 18.

LIFE HISTORY..—Immature larvae: September 8.

Adults mostly emerged November and December (acc. Weld), and January 20 (Kinsey).

In 1920 I found the conspicuously striped galls of this species abundant in the Apache Trail area of Central Arizona. The material from which Weld described the species was collected just north of that same area.

From a gall which I collected in 1929 in the southwestern corner of Utah (Zion Park), I cut a well-developed adult which seems to differ from a paratype of capronae which Mr. Weld has lent me only in having darker wing veins and heavier spotting in the cubital cell. But in the original description it is noted that this spotting varies in the type series, and I should not question the identity of the Central Arizona and Southwestern Utah material if it were not that the gall from which my lone Utah insect was cut is without stripes, although somewhat marbled. My Utah specimens, however, were collected early in September, when the galls were very young and succulent; and it is possible (though by no means established) that the markings of the typical capronae gall do not develop until the structure is more mature. Weld's material and my 1920 material was collected when most of the insects had emerged, and my 1929 material when most of the larvae were too immature for breeding. We know some other cynipids which range from Central Arizona into Southwestern Utah, on Q. subturbinella, which is the host of capronae; but we cannot be entirely certain of the range of capronae until we can secure larger series of adults.

This oak on which capronae occurs is a peculiar, prickly leaved scrub that pushes further out onto the desert in Southwestern Utah and adjacent Arizona (and Nevada?) than any other oak which I know in the United States. All of the affinities of the oak are in California. Its isolated occurrence east of the Great Basin must be connected with the moist period which that region enjoyed during the late Pleistocene. At that time several members of the California flora and fauna advanced east ward across a region that is now too dry to support any oak. Every cynipid found on Quercus subturbinella is, therefore, of especial interest in the interpretation of our Southwestern faunas and floras. In this particular case the host is Californian, but the insect entirely Rocky Mountain in its affinities. It would appear that the morphologic mutations by which this insect was separated from the other complexes of Atrusca must have been accompanied by as unique physiologic mutation which led to the insect's selection of its host. Moreover, it isapparent that these mutations must be of recent date. They must have occurred since the above-mentioned period in the late Pleistocene.

Cynips capronae shows most of the characters found in the adjacent species of the dugèsi complex. It differs from most of the others in having a much shorter, more nearly triangulate hypopygial spine, a broad anterior depression of the scutellum which is divided by a fine but distinct carina, and a gall which is prominently striped. Note that the species occurs at one edge of the range of that complex, in an area and on an oak from which no other species of the complex is known. It is clearly a geographic segregate derived from C. simulatria by fairly direct though amaterial mutation. We have debated the desirability of recognizing these larger mutations by creating a distinct complex for capronae. If we did, it would certainly emphasize the fact that a complex may arise in the same fashion as species arise from each other within a group. To keep the species in the dugèsi complex is to emphasize the fact that degree of difference is no indicator of the number of times a species is removed from another in evolution. The phylogenetic interpretation seems clear; the manner in which we translate that story into the taxo nomic nomenclature is not so important.

Capronae is ruled out of the bella complex by its much lighter wing markings (including the virtual absence of spots in the radial cell), and by the important fact that there is a species, vanescens of the bella complex, in that same part of Arizona and Utah, on the same oak host.

Atrusca capronae
Striped-Oak-Apple-Gall Wasp

Hosts: Quercus turbinella

These monothalamous oak-apple galls, with their centrally located larval chambers supported by radial fibers, measure 15-20 mm in diameter. Galls usually have a white, gray, or rarely bluish background color with irregular, bold, maroon, or purple stripes.

Atrusca capronae (Weld, 1930)

Figs 137–154

Synonymy
Diplolepis capronae Weld 1930: 29, female, gall.
Cynips (dugesi) capronae (Weld): Kinsey 1936: 99, female, gall.
Atrusca capronae (Weld): Weld 1951: 637.

Types examined

HOLOTYPE female “Camp Creek, Arizona”, “W.W. Capron coll.”, red label “Type No. 42884 U.S.N.M.”, “Diplolepis capronae Weld”, deposited in USNM, examined by GM.

Material examined

Three females “USA, Arizona, Sedona, ex Q. turbinella, leg. J.A. Nicholls, 2007.10.29”; one female “USA, Arizona, Carefree, ex Q. turbinella, leg. J.R. Zimmerman, 1992.08.03; adult emerge 1992.08.13.”; two females “USA, Arizona, Bagdad, ex Q. turbinella, leg. J.R. Zimmerman, 1993.08.26; adult emerge 1993.09.05.”

Gall (Fig. 150)

Globular gall, 8.0 to 18.0 mm in diameter, attached to the midrib or a strong vein in underside of leaf; straw yellow with vertical purple streaks. The outer wall 0.5 mm thick and crinkly radiating fibers support a central larval cell.

Biology

The asexual generation is only known to induce leaf galls on Q. turbinella. Galls mature in autumn; adults emerge in late autumn–winter the same year.

Distribution

USA: Arizona

Diplolepis capronae, new species

Host. — Quercus subturbinella Trelease.

Gall. — Globular, 8 to 18 mm. in diameter, attached to midrib or strong vein on under side of leaf. Its straw-yellow color with vertical purple streaks makes it a beautiful object when fresh. The outer shell is about half a millimeter thick and crinkly radiating fibers support a central larval cell.