Melanagromyza rudbeckiae Eiseman & Lonsdale, 2021

Eiseman, Charles S., Lonsdale, Owen, Linden, John Van Der, Feldman, Tracy S. & Palmer, Michael W., 2021, Thirteen new species of Agromyzidae (Diptera) from the United States, with new host and distribution records for 32 additional species, Zootaxa 4931 (1), pp. 1-68 : 11-12

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Melanagromyza rudbeckiae Eiseman & Lonsdale

spec. nov.

Melanagromyza rudbeckiae Eiseman & Lonsdale   , spec. nov.

( Figs. 13–15 View FIGURES 13–23 , 105–110 View FIGURES 105–110 )

Holotype. USA. IOWA: Winneshiek Co., Meadow Farm , 20.viii.2017, em.?, J. van der Linden, ex Rudbeckia laciniata   , # CSE4664 , CNC1135655 View Materials (1♁).  

Paratypes. USA. WISCONSIN: Grant Co., Thomas Wet. Prairie , 23.ix.1997, A.H. Williams, stems of Rudbeckia lacinata   , T7   N R1   W Sect. 7, [host stem] stripped of leaves and inflorescences, put into sterile containers over sterile soil and netted w/hosiery, outdoors until 2.iii.1998 when tightly caged in lab, em. 15–24.iv.1998, CNC934510–934512 View Materials   (2♁, WIRC; 1♁, CNC).

Etymology. The specific epithet refers to the host plant genus, Rudbeckia L.  

Host. Asteraceae   : Rudbeckia laciniata L.  

Larval biology. Internal stem borer.

Puparium. Formed within the stem.

Phenology and voltinism. Pupae overwinter, with adults emerging after six to eight weeks of exposure to warm temperatures in spring. The holotype was reared from a larva or pupa collected in mid-August, but unfortunately its emergence date was not recorded.

Distribution. USA: IA, WI.

Adult description. Wing length approximately 2.3–2.5 mm (♁). Female unknown. Length of ultimate section of vein M 4 divided by penultimate section: 0.7–0.8. Eye height divided by gena height: 3.6–4.8. First flagellomere small, rounded. Orbital plate slightly projecting. Gena horizontal on posterior half, angled upwards on anterior half. Face with very shallow ridge. Clypeus rounded. Head distinctly higher than long, not as developed anteriorly as in most congeners; many fibers trapped under setae on head, obscuring much of frons. Thorax subshining. Right foreleg and left hindleg missing.

Chaetotaxy: Three ori (anterior seta nearly flat on frons), two ors. Orbital setulae in several rows, mostly erect to proclinate on outer row, mostly reclinate on inner. Eye setose dorsomedially, relatively dense in paratypes, sparse in holotype. Postvertical seta slightly longer than ocellar. Two strong dorsocentral setae. Acrostichal setulae in eight rows. One smaller additional seta on katepisternum. Mid tibia with two posteromedial setae, only one on left leg of holotype.

Coloration: ( Figs. 13–15 View FIGURES 13–23 ) Setae dark brown. Color dark brown, including halter; slight metallic green shine on dorsum of thorax that is also evident and slightly more pronounced on abdomen. Calypter margin and hairs yellow.

Genitalia: ( Figs. 105–110 View FIGURES 105–110 ) Epandrium with minute posteroventral spine. Surstylus shallow, wide, curved, fused to anteroventral surface of epandrium; inner distal margin with scattered tubercle-like setulae. Cercus large, welldeveloped. Hypandrium relatively wide, sides slightly converging apically to narrower apical apodeme; inner lobe Y-shaped with sockets on anterior process. Phallophorus with base abruptly constricted, short and with sides flared; swollen distoventrally. Basiphallus U-shaped, long dorsally, pointed at ends; distant from basiphallus+mesophallus, with intervening gap nearly as long as phallophorus. Mesophallus short, cylindrical, tapering to ventromedial point of fusion on distiphallus; base slightly exceeding that of distiphallus. Distiphallus relatively short compared to congeners, subovate in ventral view with length twice width; one pair of ventrolateral tubules flanking mesophallus; dark, thick ventromedial plate greatly swollen immediately past mesophallus; dorsal chamber small, short, widest apically with margin flared laterally, internally with one pair of spinulose pads; tubular process arising from dorsal chamber short and straight. Ejaculatory apodeme with narrow, pale blade with medial rib, short stem with long lateromedial process, and long weak tube arising from base on side opposite duct; sperm pump with wide basal sclerotization, including transverse bar that is upcurved at ends.

Comments. Another Nearctic species, Melanagromyza minimoides Spencer   , has been reared from Rudbeckia laciniata   , but the larvae feed in the seedhead rather than boring in the stem ( Spencer & Steyskal 1986; this paper), and the calypter hairs are dark brown, not yellow. Melanagromyza rudbeckiae   is the undetermined species Williams (1999) reported rearing from overwintering stems of R. laciniata   in Wisconsin, and his specimens are included here as paratypes.

Melanagromyza rudbeckiae   is a relatively small, faintly greenish species with a characteristic phallus that has the distiphallus and basiphallus widely separated, the mesophallus base slightly exceeds that of the distiphallus, and the distiphallus is relatively short with the medial tubule well exposed apically, the venter is thickly sclerotized, and in ventral view the outline is narrowly egg-shaped with the sides slightly flared distolaterally. Unlike similar Melanagromyza   identifiable from couplet 36 in Spencer & Steyskal (1986), M. rudbeckiae   has a relatively long space between the basiphallus and the distiphallus. Melanagromyza longensis   is slightly larger (wing length 2.6 mm) but otherwise externally similar (including three ori), but the distiphallus is approximate to the basiphallus. Other similar but slightly larger Nearctic species are either bluish in color ( M. hicksi Steyskal   ) or have a projecting frons ( M. angelicae   ).


Canadian National Collection of Insects, Arachnids, and Nematodes