Atrusca aggregata

Quercus arizonica, oblongifolia, toumeyi
Stem galls
Detachable
Fig 118. In fall.

Diplolepis aggregata, new species

Host.--Quercus arizonica, oblongifolia, toumeyi

Gall.--Globular oak apples, up to 35 mm in diameter, occurring in summer in clusters of sometimes as many as 12 on a twig at apex of previous season's growth. Each has an abrupt slender pedicel and usually only 2-4 galls in the cluster become well developed. The fresh galls are creamy white with a reddish blush on one side and spotted with numerous small red spots. Later they become yellowish and are often covered with a bluish bloom. The central cell is supported by a dense mass of fine silky radiating fibers and the wall is thick (0.7 mm), seven times as thick as that of the smaller unspotted leaf-gall apple of the same region, D bella.

Habitat.--AZ

Cynips (aggregata) aggregata (Weld)
agamic form

Diplolepis aggregata Weld, 1926, Proc. U.S. Nat. Mus. 68 (10): 15, fig. 3. Kinsey, 1930, Ind. Univ. Studies 84–86: 446. Houard, 1935, Marcellia 28: 99.
“Cynips howardiana Kinsey in litt., possibly C. plumbea Weld” Hoffmeyer, 1930, Ent. Meddel. Kbhvn. 17: 214.
Andricus aggregatus Hoffmeyer, 1933, Ent. Meddel. Kbhvn. 18: 247.

GALL.-Large, up to 33. mm., averaging nearer 28. mm. in diameter, with a slender, drawn-out, sharply-pointed pedicel at base; light pinkish to rose and light russet brown, often finely spotted (never striped), sometimes with a whitish or bluish puberulence; occurring singly or (more often) in large clusters; the galls inserted in cracks in the bark of young twigs. Figures 87, 89.

HOSTS.—Quercus oblongifolia, Q. arizonica, Q. sacame, Q. diversicolor [rugosa] (?), Q. grisea, Q. toumeyi (the last record acc. Weld 1926).

RANGE.-New Mexico: Hillsboro (galls, Q. grisea). Arizona: Globe. Safford (galls, Q. arizonica). Fort Grant (galls, Morrison acc. Weld 1926). Oracle (Q. arizonica, Kinsey coll. Also acc. Weld 1926, and also Holloway in Kinsey coll.). Sabino Trail in Santa Catalina Mts., 4000' (Q. oblongifolia, Q. arizonica, Q. diversicolor. Also Weld coll., and types, Chrisman coll.). Santa Rita Mts. (Q. oblongifolia, Q. ari zonica). Whetstone (Q. arizonica). Tumacacori Mts. (galls., acc. Weld 1926). Fort Huachuca (galls, Q. arizonica. Also Jacot acc. Weld 1926). Chiricahua Mts. (Q. arizonica, Weld and Hubbard, acc. Weld 1926). Pata gonia (galls, Q. tourneyi, acc. Weld 1926).

Apparently confined to the oak-inhabited mountain ranges of South eastern Arizona and Southwestern New Mexico. Figure 84

LIFE HISTORY..—Adults: Alive in gall November 26. Emerging November 5, 22, 27. Also before December 3, after January 1, on January 11, and on later dates. An insect cut from a gall on November 26 was still alive in a pill box on December 31 (acc. Weld 1926). The bulk of the emergence probably early in January.

This is the only species of the complex known from the United States. It is found only in the southeastern quarter of Arizona and in the immediately adjacent portions of New Mexico. On all of the evergreen white oaks in that area, the stem galls of aggregata are conspicuous objects forming clusters two thirds as large as a man's fist. My own collections of the species were made in 1919, but it is difficult to understand why the species was not collected earlier and described before 1926.

Aggregata finds its closest relative in C. finitima, which occurs in the adjacent state of Chihuahua, in Mexico. From finitima, aggregata is to be distinguished by having a gall which is unspotted or only finely spotted with purple. The differences between the two insects are not great but enough, especially when fortified by the gall characters, to indicate that two populations are isolated in the two regions.

Unknown #39
Necked-gall wasp

Hosts: Quercus oblongifolia

These monothalamous galls can be reddish pink, pale yellow with red spots, or dark purple-black.

Atrusca aggregata (Weld, 1926)

Figs 15–32

Synonymy
Diplolepis aggregata Weld, 1926: 15 — female, gall
Atrusca aggregata: Weld 1951: 637

Types Examined

HOLOTYPE:

• Female
• “Sta Catalina Mts., Arizon”
• “13643 Hopk US”, “Chrisman M. Colo”
• Red label: “Type No 27185 U.S.N.M.”
• “Diplolepis aggregata Weld”
• Deposited in USNM
• Examined by GM

Material Examined

• 10 females: “USA, Arizona, Chiricahua Mnts. summit, ex Q. arizonica, AZ13, gall type 38, leg. J.A. Nicholls 2007.10.26”
• 56 females: “USA, Arizona, Chiricahua Mnts. nr Portal, ex Q. arizonica, AZ14, gall type 38, leg. J.A. Nicholls 2007.10.25”
• 11 females: “USA, Arizona, Molino Basin campground, Santa Catalina Mnts., ex Q. oblongifolia, AZ15, gall type 38, leg. J.A. Nicholls 2007.10.28”

Gall (Fig. 28)

Globular oak apples, up to 35 mm in diameter, usually occurring in clusters of 2–4 (up to 12) on a twig from previous season's growth.

• Pedicel: Abrupt and slender
• Color (fresh): Creamy white with a reddish blush on one side, spotted with numerous small red dots
• Color (aged): Yellowish, often with a bluish bloom
• Structure: Central larval cell supported by a dense mass of fine silky radiating fibers
• Wall thickness: ~0.7 mm

Biology

The asexual generation is known to induce stem galls on:

• Quercus arizonica
• Q. oblongifolia
• Q. toumeyi

Mature galls collected by the end of October.

Distribution

USA: Arizona