Rhopalomyia racemicola Felt 1907

Rhopalomyia racemicola Felt 1907

Rhopalomyia racemicola Felt 1907a: 24.

Adult: Antenna with 18 flagellomeres in male, 16 in female; necks of male flagellomeres III–VII 0.75–1.00 times as long as nodes, necks of female flagellomeres absent to 0.14 times as long as nodes. Palpus 2-segmented, second segment 1.5–2.5 times as long as first, slightly tapered at tip, setose and setulose. Wing length 1.9–2.1 mm in male, 1.9 mm in female. Legs covered by brownish scales. Male terminalia (Fig. 22): gonocoxite stout, wide at base, almost square, setose, with setose mediobasal lobe; gonocoxal apodeme undivided, narrows anteriorly; gonostylus short and wide, narrows only slightly toward apex, convex along both anterior and posterior margins, setose and setulose throughout, with small brush-like tooth; aedeagus relatively narrow, conical, rounded apically; hypoproct narrows distally, with very shallow dent apically, setose and setulose; cerci separated by deep triangular notch, strongly setose and setulose. Female abdomen (Fig. 37): tergite 7 trapezoid, with two anterior trichoid sensilla and several setae posteriorly and mesolaterally; tergite 8 slender Y-shaped, proximal arms less than third the length of shaft, each with anterior trichoid sensillum; ovipositor 9.0–9.3 times as long as tergite 7.

Pupa: unknown.

Type material: Rhopalomyia racemicola Felt. Syntypes: 2 males, 2 females, USA, Asheville, NC, 16/IX/1906, E.P. Felt, ex. S. altissima (R. canadensis of Felt), Felt # a1605, deposited in Felt Collection.

Host: Solidago altissima, S. fistulosa (?)

Gall: The green, bristly, onion-shaped capitulum galls are situated among normal capitula and can sometimes be found in aggregations. They were recorded by Felt (1907a, 1915) from S. altissima in North Carolina, and Gagné (1989) reported similar galls on S. fistulosa from Florida, which he attributed tentatively to the same species. The description of the galls and the mention of previous records of this species in Felt (1915) actually refer to the galls of Schizomyia racemicola rather than those of R. racemicola (see Gagné 1971). The true nature of R. racemicola galls is therefore uncertain, and we tentatively adopt Gagné’s assumption that the galls he received from Florida are those of R. racemicola. Adults emerged in mid September in North Carolina, and in December in Florida. Given that the galls develop in capitula, we assume that R. racemicola is univoltine, but verifying the identity of the host plant and the galls, and clarifying the life history of this species require more investigation.

Remarks: Adults of R. racemicola generally resemble those of the other Rhopalomyia species from goldenrod capitula (R. anthophila, R. guttata, and R. cruziana) but this is the only species of the four whose female flagellomeres occasionally have necks, and its male gonocoxites are angular at their bases rather than rounded as in the other species. We currently consider Gagné’s record (1989) from S. fistulosa as representing R. racemicola because of the general similarity of the galls to the original description by Felt (1907a) and because the three females reared by Gagné generally resemble the R. racemicola types. Nevertheless, more information and additional material (particularly males) will need to be obtained before this assumption can be confirmed.