Rhopalomyia pedicellata 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 : 20-29

Rhopalomyia pedicellata Felt 1908

Rhopalomyia pedicellata Felt 1908: 365 .

Cecidomyia euthamiae Stebbins 1910: 53 ; Felt 1915: 262 ( Rhopalomyia )

Adult: Yellowish-white, with dark scales and hairs; Legs densely covered by fine, dark scales. Antenna with 16–17 flagellomeres in male, 16–18 in female; necks of male flagellomeres III–VII 0.47–0.67 times as long as nodes, necks of female flagellomeres absent to 0.25 times as long as nodes. Palpus 1-segmented. Wing length 2.4 mm in male, 2.2–2.8 mm in female. Ovipositor 4.8–5.2 times as long as tergite 7. Otherwise similar to R. fusiformae .

Pupa ( Figs. 52–53 ): Orange. Antennal bases round V-shaped in frontal view, with tiny pointed tips. Frons without projections or ridges, with short lateral projections, basal edge rounded.

Type material: Rhopalomyia pedicellata Felt. Syntypes: 1 male, 2 females, USA, Albany, NY, 24–26/ VII/1907, E.P. Felt, ex. E. graminifolia, Felt # a1650, deposited in Felt Collection; 1 male, USA, NY, Albany, 6/VIII/1907, E.P. Felt, ex. E. graminifolia, Felt # a1650, deposited in Felt Collection. Felt (1908) also mentioned a type labeled # 1311, but specimens associated with this number were not found.

Cecidomyia euthamiae Stebbins : Holotype: 1 gall, USA, Springfield, MA, unspecified date, F.A. Stebbins, specimen # 194, deposited in the Springfield Natural History Museum, Massachusetts ( NHSM).

Other material examined (all from E. graminifolia ): 3 females, USA, Eldridge Wilderness, West Dryden, NY, 13–14/IX/1987, M.V. McEvoy; 1 male, USA, Lewisburg, PA, 15/VIII/2005, T. Dowling; 2 exuviae, USA, Lewisburg, PA, 29/VII/2005, T. Dowling; 1 female, USA, Lewisburg, PA, Moore School Rd., 29/VII/ 2005, N. Dorchin; 2 pupae, USA, PA, Bucknell University Chillisquaque Creek Natural Area, 2/IX/2005, N. Dorchin; 1 female, 1 exuviae, USA, Mauses Creek, PA, 16/IX/2005, N. Dorchin; 1 female, USA, R.B. Winter State Park, PA, 22/VII/2007, N. Dorchin.

FIGURES 26–33. Female 7th and 8th abdominal tergites, dorsal view. 26. Rhopalomyia anthophila . 27. Rhopalomyia bulbula . 28. Rhopalomyia guttata . 29. Rhopalomyia capitata . 30. Rhopalomyia clarkei . 31. Rhopalomyia cruziana . 32. Rhopalomyia fusiformae . 33. Rhopalomyia gina . Scale bars = 0.1 mm

FIGURES 34–39. Female 7th and 8th abdominal tergites, dorsal view (unless otherwise noted). 34. Rhopalomyia hirtipes . 35. Rhopalomyia lobata . 36. Rhopalomyia inquisitor , lateral. 37. Rhopalomyia racemicola . 38. Rhopalomyia solidaginis . 39. Rhopalomyia thompsoni . Scale bars = 0.1 mm

Host: Euthamia graminifolia

Gall and biology: The gall is found on stems, leaves, or inflorescences. This is a delicate, slender, 14–21 mm long gall, carried on a pedicel that is about half as long as the remainder of the gall (hence the species’ name) ( Figs. 84–85 ). The gall is single-chambered, green to purplish-red, with longitudinal ridges, and tapered at both ends. The internal walls of the gall are smooth and shiny and the larva is usually found facing downwards at the bottom of the chamber. Galls are common and found from mid June to September. The gall reaches its final size when the larva is still a first instar. The species completes at least two generations per year, with adult emergence from July to September. The structure of the gall is identical to that of R. fusiformae except for the presence of the pedicel.

Remarks: Rhopalomyia pedicellata and R. fusiformae are similar in adult morphology but can be reliably distinguished from each other based on their pedicelled and sessile galls, respectively. No galls of intermediate morphology were found, and a recent molecular analysis suggests that the two species are valid (Dorchin et al., in prep.). Pupae of R. pedicellata differ from those of the related R. lobata , also on E. graminifolia , in having small, pointed tips on the antennal bases that are absent in R. lobata , and in lacking the pronounced, lateral projections of the frons. The pupae of R. fusiformae are unknown.

Figures

FIGURES 48 – 55. Pupal heads. 48. Rhopalomyia hirtipes, ventral. 49. Rhopalomyia hirtipes, lateral. 50. Rhopalomyia lobata, ventral. 51. Rhopalomyia lobata, lateral. 52. Rhopalomyia pedicellata, ventral. 53. Rhopalomyia pedicellata, lateral. 54. Rhopalomyia solidaginis, ventral. 55. Rhopalomyia solidaginis, lateral. Scale bars = 300 μm

FIGURES 78 – 85. Rhopalomyia galls. Figs. 78 – 81. Rhopalomyia lobata. 78. Young gall in apical meristem. 79. Young galls in lateral meristems (arrows). 80. Mature gall showing modified, broad leaves sheathing the fleshy gall center. 81. Mature gall showing exposed, fleshy center after onset of adult emergence. Figs. 82 – 83. Rhopalomyia fusiformae; 82. Aggregation of galls on stem and leaves (arrows). 28. Gall, showing longitudinal ridges and lack of pedicel. Figs. 84 – 85. Rhopalomyia pedicellata. 84. Group of galls situated on long pedicels among capitula. 85. Gall arising from stem, carried on long pedicel.