Ophiomyia rugula Eiseman & Lonsdale, spec. nov.

(Figs. 29–31, 70–72, 127–132)

Holotype. USA. NORTH CAROLINA: Durham Co., Durham, Leigh Farm Park, 29.iv.2018, em. 17.v.2018, T. S. Feldman, ex Baccharis halimifolia, # CSE4553, CNC1135680 (1♁).

Paratype. Same data as holotype, CNC1135681 (1♁); Wake Co., Morrisville, Lake Crabtree County Park, 12.vii.2018, em. 13.vii.2018, T. S. Feldman, ex Baccharis halimifolia, # CSE4951, CNC934530 (1♁).

Etymology. The specific epithet (L. rugula —a small wrinkle) refers to the appearance of the larval feeding site as a small wrinkle in the leaf.

Host. Asteraceae: Baccharis halimifolia L.

Leaf mine. (Figs. 70–72) Mostly green and interparenchymal, consisting of a short, narrow wrinkle along the midrib. In some examples the mine is confined to the basal portion of the midrib, and in others the basal portion appears to have been mined but the mine is only conspicuously wide or wrinkled at or somewhat beyond the middle of the leaf.

Puparium. (Fig. 72) White; centered on the midrib in the distal end of the mine.

Phenology and voltinism. This species is evidently at least bivoltine, with larvae feeding in April emerging as adults in mid-May, and with adults of another generation emerging in mid-July.

Distribution. USA: NC.

Adult description. Wing length 2.3–2.4 mm (♁). Female unknown. Length of ultimate section of vein M 4 divided by penultimate section: 0.8. Eye height divided by gena height: 6.2–6.5. First flagellomere subcircular with slightly longer hairs on anterodorsal margin. Orbital plate very narrow. Ocellar triangle slightly shinier, ending near level of anterior ors. Face with shallow, rounded ridge. Gena rounded anteriorly, only slightly extending past anterior margin of eye; neither pointed nor projecting. Lunule somewhat semicircular with wide medial groove. Palpus narrowed basally. Clypeus with narrow, truncated apical margin with sharp corners. Thorax subshining.

Chaetotaxy: One ori, three ors; anterior ors slightly shorter than other fronto-orbitals; paired setae not equally positioned on both sides. Single row of orbital setulae. Ocellar and postvertical setae subequal to posterior ors. Two strong dorsocentral setae. Eight rows of acrostichal setulae. Katepisternum with several enlarged dorsal setae, including one nearly as long as dominant seta. Mid tibia with two posteromedial setae.

Coloration: (Figs. 29–31) Setae dark brown. Body dark brown with halter stem light brown with dark patches. Calypter margin and hairs dark brown.

Genitalia: (Figs. 127–132) Surstylus broad, rounded, fused to epandrium, with short, pointed tubercle-like setae along inner-distal margin. Cercus large, well-developed. Hypandrium stout medially; inner lobe V-shaped, nearly smooth. Phallophorus cylindrical, weakly connected dorsally to basiphallus; phallus past phallophorus angled ventrally. Basiphallus with short, wide, thin dorsal sclerite, laterally produced into one pair of long sinuate ventral bands and one pair of more dorsally positioned pockets. Mesophallus lightly sclerotized, straight, resembling slightly thickened terminal section of ejaculatory duct. Distiphallus band-like, dorsoventrally compressed, slightly wider than mesophallus (both weakly differentiated in ventral view), which is inserted medially on ventral surface. Additional small U-shaped sclerite suspended in membrane ventral to apex of mesophallus of uncertain homology.

Comments. Ophiomyia rugula is clearly related to O. similata (Malloch) based on genitalic structure, and is indistinguishable from it externally, although O. similata has one or two mid tibial setae and most of the type series has smaller fronto-orbitals that are less than half the width of the frons (not slightly more). The genitalia of O. similata differ in lacking the ventrolateral bands of the basiphallus, the distiphallus is wider and higher, and the suspended ventrodistal sclerite of uncertain origin is thicker and more distally positioned.

The immature stages of Ophiomyia similata are unknown, but O. abutilivora (discussed above) belongs to a related lineage, and it forms a characteristic gall-like raised mine or “welt” in the stem of Abutilon theophrasti (Malvaceae). Ophiomyia tiliae (Couden) also belongs to this lineage, and it forms galls in twigs of Tilia americana L. (Malvaceae) (Spencer & Steyskal 1986). The feeding damage of O. rugula is also gall-like, and it may be that O. similata and allied species of the California O. jacintensis group (see Spencer & Steyskal (1986: 37)) will prove to have similar larval biology.

The only Ophiomyia previously associated with Baccharis is O. spicatae Spencer, known from a single female reared from a stem mine on B. spicata (Lam.) Baill. in Brazil (Spencer 1963).