Dryocosmus coxii

Quercus emoryi, hypoleuca [hypoleucoides]
Stem galls
Stem swellings
Fig 44.

Dryocosmus coxii

Cynips coxii
Andricus coxi
Andricus bassettianus
Plagiotrichus coxii

The writer has collected the common fusiform stem swelling of this species on Quercus emoryi at Fierro, Kingston, and in the Burro Mountains, N. Mex.; in the Chiricahua, Huachuca, Mule, Patagonia, Tumacacori, Santa Rita and Santa Catalina Mountains, and at Bisbee, Nogales, Oracle, and Prescott, Ariz. The galls were seen on Quercus hypoleuca in the Santa Catalina, Patagonia, Huachuca, and Mule Mountains and at Fierro and Kingston. In April, June and July only old galls were found. E. Jacot collected a fresh gall in the Huachucas September 17, too immature to rear. The writer collected mature fresh galls on emoryi at Oracle on December 17 containing both pupae and adults which emerged January 4-24. Galls on emoryi from the Mule Mountains collected early in December gave adults December 31, January 13, 24, February 4 and 14. These flies run to Dryocosmus in the Tierreich key.

Dryocosmus coxii
Stem-gall wasp

Hosts: Quercus emoryi, hypoleucoides

Galls are bark-gray, woody, and hard.

Range: Payson AZ

Kokkocynips coxii (Bassett, 1881) n. comb.

Cynips coxii Bassett, 1881. Canad. Ent., vol. 13, p.112. [Syn. by Kinsey, 1922: 123-125].
Andricus coxii (Bassett), Ashmead, 1885. Trans. Amer. Ent. Soc., vol. 12: 295.
Andricus coxi Bassett, 1900. Trans. Amer. Ent. Soc., vol. 26, p.320.
Andricus bassetianus Dalla Torre and Kieffer, 1902. in Wytsman Gen. Ins. Hym. Cynipidae, p.61. [Syn. by Kinsey, 1922: 123-125].
Plagiotrichus (sic.) coxii (Bassett), Kinsey, 1922. Ind. Univ. Stud. 53, pp.122-5.
Plagiotrochus coxii var translatus Kinsey, 1922: 126 n. syn.
Dryocosmus coxii (Bassett): Weld, 1926b. Proc. U.S. Nat. Mus., 68(10): 41.
Dryocosmus coxii var translatus (Kinsey) Weld, 1951: 646.

Gall: the galls are elongate to globose twig swellings up to 20 mm. in diameter and 65 mm in length; on older twigs from previous years’ growth. Multilocular, smooth surface covered with normal bark. Larval cells closely embedded in the less solid part of the tissue (Kinsey 1922).

Host plant: Quercus emoryi and Quercus hypoleucoides (=hypoleuca Engelm.).

Biology: only known from an asexual generation. The original source is somewhat imprecise about gall phenology, saying that the whole life cycle takes more than one year, as the insects emerge in midwinter and the young galls appear immediately.

Distribution: Arizona, New Mexico and possibly Texas (Kinsey 1922).

Remarks: Kinsey (1922) transferred this species described by Bassett to the genus Plagiotrichus (sic.) (=Plagiotrochus Mayr) under the mistaken belief that this genus, described from the Western Palaearctic, was also present in North America. In his account of this species Kinsey gave a short re-description, summarized the data on biology and distribution, and described two new varieties. Kinsey (1922) emphasized the particularity of this species as he had some doubts about its correct generic placement, but his placement was finally made based on the structure of the gall. Weld later transferred the species to Dryocosmus, on the basis that “the flies run to Dryocosmus in the Tierreich key” (a reference to the work by Dalla Torre and Kieffer (1910); Weld 1926b).

Plagiotrichus coxii

GALL. — A globose to elongate, solid twig gall. Polythalamous, averaging twenty or more cells to a gall. Smooth, covered with nearly normal bark, somewhat reddened; up to 20. mm. in diameter and 65. mm. in length. Internally rather solid but not entirely so, the larval cells with a distinct lining-, closely embedded in the less solid part of the tissue. On black oaks.

RANGE, — Arizona. Possibly also in New Mexico, western Texas, and Mexico, wherever Q. Emoryi, Q. hypoleuca, and related oaks occur.

The insect of this species is in several respects, particu- larly the almost naked mesonotum and the 14-segmented, short antennse, extreme for this genus. But species like P. suttonii and P. perdens of California are intermediate between coxii and the white oak species of the genus. This empha- sizes the artificial nature of our sharp generic lines. I doubt whether I should consider the species in this genus except for the additional evidence furnished by the gall. It is typically a Plcigiotrichus gall, related more closely to the other black oak species, as is the insect also, than to any other white oak species.

The insects emerge in midwinter, December and January. The young galls appear immediately, which suggests that they arise from an alternate generation, the whole life cycle taking more than one year.

I have galls from New Mexico which may belong to this species, but rather extensive collecting in both western Texas and New Mexico failed to give me other galls of this species. If the species occurs in those states, it certainly does not there reach the abundance with which it infests the black oaks of southern Arizona.

[Kinsey describes a distinct variety on each of this gall's two hosts; see paper for details]