Atrusca cava (Weld, 1926)

Figs 169–172

Synonymy
Diplolepis cava Weld, 1926: 22, female, gall.
Cynips (Atrusca) (dugesi) cava (Weld): Kinsey 1930: 293, female, gall.
Cynips (dugesi) cava (Weld): Kinsey 1936: 103, female, gall.
Atrusca cava (Weld): Weld 1951: 637.

Types examined

HOLOTYPE female Diplolepis cava “Austin, Tex., Dec. 4, 1917”, “Quercus breviloba”, “Diplolepis cava Weld” red label “Type No. 27189 U.S.N.M.”, deposited in USNM, examined by GM.

Gall (Fig. 172)

A bulboid gall, 14–20 mm in diameter, usually single on underside of leaf. Reddish-brown, not spotted, with thin walls, central cell supported by numerous silky fibers (gall pics from Weld, 1959).

Biology

The asexual generation is only known to induce leaf galls on Q. sinuata (= Q. breviloba). Galls mature in late autumn; adults emerge next year in spring.

Distribution

USA: Texas.

Atrusca cava

Quercus breviloba, laceyi
Leaf galls, detachable
An oak apple, 14-20 mm in dia, usually single on under side of leaf in fall, not spotted.

[Photo caption]
On Q breviloba. Pupae had transformed by Nov 26 and adults had chewed out of the inner cell in Dec. Normal emergence date unknown.

Diplolepis cava, new species

Host. — Quercus breviloba and Quercus laceyi.

Gall (fig. 5). — An oak apple, 14-20 mm. in diameter, usually single on under side of leaf in fall. Reddish-brown, not spotted, wall thin, central cell supported by numerous silky fibers, a definite bundle of parallel fibers from cell to point of attachment of gall.

Habitat.—The type material was collected in October 1917, near Austin, Tex., on the shin oak, Q. breviloba. A gall opened November 10, contained a pupa which transformed November 26. By December 4, adults had chewed out of the inner cell and were found among the radiating fibers. The normal emergence date unknown. These galls were seen also at Boerne and Kerrville. A paratype fly came from a gall on Q. laceyi at Boerne, the gall containing a pupa on November 20, which transformed by December 7.

Cynips (dugèsi) cava (Weld)
agamic form

Diplolepis cava Weld, 1926, Proc. U.S. Nat. Mus. 68 (10):22, fig. 5.
Cynips cava Kinsey, 1930, Ind. Univ. Studies 84-86:293, figs. 46, 260-261,270, 283. Houard, 1934, Marcellia 28:38. Houard, 1935, Marcellia 28: 110

GALL.-Similar to other galls of the C. bella and C. dugèsi complexes, but gourd-shaped instead of spherical, having a short, rather stout, drawn out, more or less cylindric base which is up to 3.0 mm. in length and 3.0 mm. in diameter; body of gall up to 22.0 mm. in diameter. Young galls light yellow with a rosy tinge, older galls becoming light russet brown, unspotted or only obscurely spotted. Figure 9.

HOST.-Quercus breviloba, Q. breviloba f. laceyi.

RANGE.-Texas: Austin (type, Weld coll.; also Patterson in Kinsey coll.). Round Rock. Leander. Boerne and Kerrville (acc. Weld 1926). Probably restricted to a limited area in Central Texas, extending mostly west from Austin. Figure 18

LIFE HISTORY..—Galls: Young on June 7. Pupae: November 10, 20. Adults: November 25, 26. December 4, and before and after December 8.

The gall differs from those of all the northern species of dugèsi in being stalked to bulboid in shape. Taken together, these differences would seem enough to warrant recognition of the distinct complex in which we cataloged this species in our 1930 monograph. But the potentialities for all of the cava characters are in the dugèsi complex. This is evidenced by their appearance, singly, or in limited combinations, in one place or another within that complex; and the geographic position of cava also indicates that it is a geographic segregate of the dugèsi complex. Whatever we do with the species for the convenience of our cataloging, it seems certain that cava is, phylogenetically, no further removed from simulatria than simulatriæ is from the next species within the list. Such extreme developments of the dugèsi complex as cava, brevipennata, capronae, and others give evidence of the essential identity of the processes by which both species and higher categories come into existence.

Cynips catena is the closest relative of cava. Catena is clearly an offshoot of the same stock which has moved further west into a single mountain range east of the town of Alpine, in West Texas. Cava is distinct from catena in being brighter rufous in color, in having a shorter hypopygial spine, rather distinctly shorter wings, a slightly smaller areolet, and a stalked-bulboid gall.

Cynips (Atrusca) cava
agamic form

Diplolepis cava

GALL. — A large, gourd-shaped leaf gall with a spherical body, with fine, dense fibers supporting the central larval cell. Monothalamous. Most of the gall strictly spherical, up to 22.0 mm. in diameter, drawn out into a short, rather stout, more or less cylindrical base which may be as much as 3.0 mm. in length and 3.0 mm. in diameter; the surface essentially smooth but not very shining, microscopically shagreened; young galls light yellow with a rose tinge; older galls becoming light russet brown, unspotted; the outer shell rather thin but hard and brittle when dry. Internally filled with silky, moderately dense (but not packed), branching fibers which hold the larval cell centrally; some short, incomplete fibers also on the inner wall of the outer shell and on the larval cell; the cell up to 3.5 mm. in diameter. Attached by a fine point at the bottom of the drawn-out base; on the upper or ('more often) the under surfaces of leaves of Quercus breviloba and its form laceyi. Figures 260-261.

RANGE. — Texas: Austin (type, Weld coll.; also Patterson in Kin- sey coll.). Round Rock and Leander (Kinsey coll.). Boerne and Kerr- ville (acc. Weld 1926). , Probably restricted to a limited area in Texas, extending mostly west from Austin. Figure 46.

This gall closely resembles the galls of the related species bella and dugesi, but differs in having a drawn-out, blunt base. Patterson found young galls as early as June 7 (in 1921). The galls develop thru the summer and fall, the adults maturing and chewing out of the larval cells sometime before emergence from the outer walls of the galls. On November 10 and 20 Weld found pupae which transformed on November 26 and later. He found adults among the radiating fibers in the galls by December 4. Patterson found live adults in this condition on November 25 (in 1921). By early De- cember most of the galls have fallen from the trees, in many cases still attached to the dead leaves, and some of the adults begin emerging then, altho my collections made on December 6 and 8 (in 1919) still contained many adults which did not emerge until later.

Several of the cynipid species which occur just northwest of Austin are confined to the Texan post oak, Quercus breviloba, and it is possible that we will not find cava on any other host.

The insect is close to Cynips bella and dugesi. Cava might be considered a variety of dugesi , but its median depression on the scutellum, its nearly unspotted wings, and more particularly its distinctive gall leads to my conclusion that it is a distinct species. Cynips cava and Cynips dugesi are the only insects in this genus which have shortened wings in which the reduction is less than forty per cent of the wing length normal for the subgenus.