Rhopalomyia gina Dorchin

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 : 13

Rhopalomyia gina Dorchin n.sp.

Adult: Antenna with 16–17 flagellomeres in both sexes; last two flagellomeres often partially fused or the apical flagellomere “budding” from the subapical one; necks of male flagellomeres III–VII 0.75–0.82 times as long as nodes ( Fig. 6 ), necks of female flagellomeres III–VII 0.20–0.22 times as long as nodes ( Fig. 7 ). Palpus 1-segmented, tapering toward apex, with several long setae. Wing length 2.5–3.2 mm in male, 2.2–2.6 mm in female, covered by dark, hair-like scales. Claws untoothed, empodia longer than claws ( Fig. 5 ). Male abdomen: tergites 1–7 with posterior row of setae, band of setae mesally, a pair of anterior trichoid sensilla, and evenly covered by dark, hair-like scales. Tergite 8 with fewer long setae. Sternites weakly sclerotized, with posterior and mesal groups of setae and pair of adjacent trichoid sensilla anteriorly. Male terminalia ( Figs. 18–19 ): gonocoxite cylindrical, setose and setulose, with prominent, strongly setose and sclerotized mediobasal lobe bearing several setose apical papillae; gonocoxal apodeme bilobed; gonostylus cylindrical, setose and setulose throughout, with small brush-like tooth; aedeagus wide, cylindrical; hypoproct with very shallow notch, or entire in some individuals, evenly setulose; cerci separated by deep notch, setose and setulose. Female abdomen (Fig. 33): tergites 1–7 with posterior row of setae, several scattered long setae elsewhere, and evenly covered by dark scales; tergite 8 Y-shaped, wide and short, with few long setae; all tergites with two anterior trichoid sensilla. Sternites very weakly sclerotized or completely unsclerotized, with long setae mesally and a pair of adjacent trichoid sensilla anteriorly; ovipositor 4.1–5.5 times as long as tergite 7; cerci fused into single cylindrical lamella, setose and setulose ( Fig. 8 ); hypoproct rounded apically, strongly setose and setulose.

Pupa ( Figs. 46–47 ): Light orange. Antennal bases developed into tapering, anteriorly pointed horns with a longitudinal fold-like groove closer to lateral than to median edge of horn. Posterior margins of antennal bases rounded in frontal view. Frons without median projections or ridges, with pronounced lateral projections, posterior edge with a V-shaped extension in frontal view. Cephalic seta short. Abdominal segments dorsally and laterally with pointed spicules. Terminal abdominal segment divided longitudinally into two lobes.

Type material: Rhopalomyia gina Dorchin. Holotype: male, USA, Mauses Creek, PA, 30/V/2008, C. Blair, ex. leaf gall on S. juncea , deposited in USNM. Paratypes: All from USA, PA, Mauses Creek, collected and reared from leaf galls on S. juncea . 2 pupae, 7/VI/2007, G. Lee; 2 males, 20/V/2008, C. Blair; 2 females, 1 male, 23/V/2008, C. Blair; 5 females, 2 males, 26/V/2008, C. Blair; 8 females, 6 males, 30/V/ 2008; 2 pupae, 11/VI/2008, C. Blair.

Etymology: The species is named after Gina Lee, who discovered the galls in June of 2007 during her undergraduate summer internship at Bucknell University. The name is a noun in apposition.

Host: Solidago juncea

Gall and biology: Galls of this species ( Fig. 68 ) are similar in appearance to galls of R. clarkei on S. rugosa ( Figs. 62–64 ) and of its close relative on S. gigantea ( Fig. 67 ). They are 2.8–5.0 mm long and 0.6–1.3 mm wide at widest part (n=22), smooth and green, often with purplish longitudinal lines and tip, and are most often found on the upper side of leaves. The position of the gall is usually apparent on the other side of the leaf only as a small scar, but some galls had a long, curly appendage extending from that side ( Fig. 69 ). Galls were found in mid May to mid June and adult emergence began in early June, with a sex ratio of 2: 1 in favor of females. The galls were heavily attacked by ectoparasitoids (65% parasitism in 2007, n=22 galls), but in May 2008 the parasitism rate was only 12% (n= 41 galls). Further examination of the plants in early August failed to reveal any galls, but Gagné (1989 and pers. com.) found similar galls in late September on leaves subtending and composing the rosette galls of Asphondylia monacha on S. juncea in Silver Spring, MD. It therefore appears that this species completes at least two generations per year.

Remarks: This species is similar to R. clarkei and R. inquisitor in the morphology of adults and galls, but tergite 8 of the female abdomen is considerably wider and shorter in R. gina (Fig. 33), and the male gonopods are more slender and therefore resemble those of the three Rhopalomyia species from Euthamia ( R. fusiformae , R. lobata , and R. pedicellata ). All of these species share the one-segmented palpus, presence of necks in the female flagellomeres, and two-armed gonocoxal apodeme in the male. The pupa of R. gina differs from that of R. clarkei in having lateral projections of the frons, which are also present in R. lobata , and is unique for the longitudinal groove along the antennal bases.

Figures

FIGURES 1 – 8. 1 – 3. Rhopalomyia guttata; 1. Male distal flagellomeres. 2. Female distal flagellomeres. 3. Mouthparts. 4. Rhopalomyia anthophila mouthparts. Figs. 5 – 8. Rhopalomyia gina; 5. Acropod. Scale bar = 0.05 mm. 6. Male head with 5 proximal flagellomeres. 7. Female head with 5 proximal flagellomeres. 8. Tip of female ovipositor showing fused cerci and hypoproct. Scale bars (except for Fig. 5) = 0.1 mm.

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

FIGURES 40 – 47. Pupal heads. 40. Rhopalomyia anthophila, ventral. 41. Rhopalomyia anthophila, lateral. 42. Rhopalomyia capitata, ventral. 43. Rhopalomyia capitata, lateral. 44. Rhopalomyia clarkei, ventral. 45. Rhopalomyia clarkei, lateral. 46. Rhopalomyia gina, ventral. 47. Rhopalomyia gina, lateral. Scale bars = 200 μm

FIGURES 62 – 69. Rhopalomyia leaf and stem galls. Figs. 62 – 64. Rhopalomyia clarkei galls on Solidago rugosa; 62. Young gall. 63. Mature galls. 64. Galls on underside of leaf. 65. Rhopalomyia clarkei galls on stem and leaf of Solidago altissima (photo by M. Wise). Figs. 66 – 67. Rhopalomyia sp. galls on leaves of Solidago gigantea; 66. Very young galls. 67. Mature gall. Figs. 68 – 69. Rhopalomyia gina galls on leaves of Solidago juncea. 68. Gall on upper side of leaf. 69. Tail-like appendage of gall on underside of leaf.