Rhopalomyia bulbula Felt 1908

Dorchin, Netta, Mcevoy, Miles V., Dowling, Todd A., Abrahamson, Warren G. & Moore, Joseph G., 2009, Revision of the goldenrod-galling Rhopalomyia species (Diptera: Cecidomyiidae) in North America, Zootaxa 2152, pp. 1-35 : 7-8

Rhopalomyia bulbula Felt 1908

Rhopalomyia bulbula Felt 1908: 365 .

Adult: Antenna with 16 flagellomeres in male, 15–16 in female; necks of male flagellomeres III–VII 0.61–0.65 times as long as nodes, female flagellomeres without necks. Palpus 1-segmented, fusiform, tapered, more than twice as long as wide, setulose with few long setae. Wing length 3.2 mm in male, 2.9 mm in female. Empodia as long as claws. Male abdomen covered by dark scales. Male Terminalia ( Fig. 11 ): gonocoxite robust, setose, with strongly setose mediobasal lobe; gonocoxal apodeme broad and truncate, undivided; gonostylus short and bulky, anterior margin straight, posterior margin evenly curved, setulose throughout, with small, brush-like tooth; aedeagus conical, rounded apically; hypoproct entire, wide, truncate, setose and setulose; cerci separated by a shallow notch, setose and setulose. Female abdomen (Fig. 27): covered by dark, fusiform scales; tergites 1–6 rectangular; tergite 7 X-shaped, setose on most of surface; tergite 8 very narrowly Y-shaped, with two anterior trichoid sensilla and few setae on proximal half; ovipositor 11.1 times as long as tergite 7.

Pupa: unknown.

Type material: Rhopalomyia bulbula Felt. Syntypes: 1 male, 1 female, USA, Worcester, MA, unspecified date, M.T. Thompson, ex. S. juncea, Felt # 1115, deposited in Felt Collection.

Host: Solidago juncea

Gall and biology: Galls are found in clusters of 3–15 on rhizomes, at the base of spring shoots. The gall is single-chambered, resembles a bud, with acute apex and base, 4.5–6.0 mm long and 1.5–2.5 wide. The surface of the gall is smooth and white, with green stripes where it is exposed to light. Adults emerge in late May ( Thompson 1915). No second generation has been found during summer and fall.

Remarks: Both R. bulbula and R. hirtipes develop at the base of shoots on S. juncea . Given that R. bulbula is known only from a spring generation whereas R. hirtipes is known only from a fall generation, the idea that these may represent the spring and summer generations of the same species is appealing ( Felt 1915). However, numerous morphological differences in both males and females render this option less plausible: Rhopalomyia bulbula is a smaller species, and has 15–16 antennal flagellomeres and neckless female flagellomeres as opposed to the 20–22 flagellomeres and relatively long necks of the female flagellomeres in R. hirtipes . Furthermore, R. bulbula has 1 rather than 2 palpal segments, its male gonocoxite lacks the apical mesoventral lobe that is present in R. hirtipes , its gonopods are not as robust and spherical as those of R. hirtipes , and its ovipositor is much longer. Although all these differences are based on the single available couple of R. bulbula , originally described by Felt in 1908, it seems unlikely that a larger sample size will diminish them. We therefore assume that R. bulbula induces a second generation gall that is yet to be found.

Figures

FIGURES 9 – 19. Male terminalia (in dorsal view unless otherwise noted). 9. Rhopalomyia anthophila. 10. Rhopalomyia anthophila, left gonopod, ventral. 11. Rhopalomyia bulbula. 12. Rhopalomyia guttata. 13. Rhopalomyia capitata. 14. Rhopalomyia clarkei. 15. Rhopalomyia cruziana. 16. Rhopalomyia fusiformae. 17. Rhopalomyia hirtipes. 18. Rhopalomyia gina. 19. Rhopalomyia gina, lateral. Scale bars = 0.1 mm