Agromyza indistincta, Eiseman & Lonsdale & Feldman, 2019

Eiseman, Charles S., Lonsdale, Owen & Feldman, Tracy S., 2019, Nine new species of Agromyzidae from North Carolina, USA, with new host and distribution records for additional species, Zootaxa 4571 (3), pp. 301-333: 304-305

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Agromyza indistincta

spec. nov.

Agromyza indistincta   spec. nov.

( Figs. 3–4 View FIGURES 1–6 , 28 View FIGURES 26–32 , 57–63 View FIGURES 57–63 )

Holotype. NORTH CAROLINA: Durham Co., Durham, Leigh Farm Park , 9.v.2017, em. 9–, T.S. Feldman, ex Dichanthelium   , # CSE3807, CNC939776 View Materials (1♂).  

Paratypes. Same data as holotype, CNC939775 View Materials ,   CNC939777 View Materials (2♀)   .

Etymology. The specific epithet refers to the similarity of both the leaf mine and the adult to those of other Agromyza   species on the same host plant.

Host. Poaceae   : Dichanthelium (Hitchc. & Chase) Gould.  

Leaf mine. ( Fig. 28 View FIGURES 26–32 ) Similar to the mine of Agromyza arundinariae   described above. Two of the specimens were reared from one mine and the third was reared from a solitary larva in a separate leaf.

Puparium. ( Fig. 4 View FIGURES 1–6 ) Brown; formed outside the mine.

Distribution. USA: NC.

Adult description. Wing length 2.2 mm (♂), 2.8–2.9 mm (♀). Costa extending to M 1. Length of ultimate section of vein M 4 divided by penultimate section: 0.8–0.9. Eye height divided by gena height: 6.6–10.1. First flagellomere small, rounded; distal margin with slightly longer hairs, medially with small denser circular tuft. Face with shallow carina. Male frons rounded and slightly projecting anterodorsally. Ocellar triangle slightly longer than wide, apex somewhat rounded and nearly reaching level of anterior ors. Ocellar triangle and orbital plate slightly shinier. Thorax subshining.

Chaetotaxy: Two ors, two ori, becoming slightly shorter anteriorly; male and one female with additional smaller, thinner ori on one side; one female with three ori on both sides. One row of orbital setulae. Ocellar and postvertical setae subequal to fronto-orbitals. Two dorsocentral setae, anterior seta slightly shorter. Acrostichal seta strong, as long as anterior dorsocentral. Acrostichal setulae in eight straight to irregular rows. Mid tibia with two strong posteromedial setae.

Coloration: ( Fig. 3 View FIGURES 1–6 ) Setae dark brown with paler brown shine. Body mostly dark brown with halter white; frontal vitta (excluding ocellar triangle) brown; female orbital plate (excluding around base of setae) and parafacial paler brown, sometimes whitish; antenna brown with inner surface of pedicel paler, and first flagellomere darker brown distally and yellowish basally on inner surface; gena brown with ventral margin dark brown; male antennal groove paler dorsally; female with minute faded light yellow to whitish spot at anterior corner of scutellum and with similarly pale region above wing base; apex of fore femur very narrowly light yellow; posteromedial surface of hind femur pale and desclerotized; base of fore tibia yellow, with length of spot exceeding width; fore tarsus light yellow, mid and hind tarsus brown with dirty white tint with hind tarsi darker. Calypter margin and hairs dark brown.

Genitalia: ( Figs. 57–63 View FIGURES 57–63 ) Epandrium wide, shallow; inner-ventral margin fused to surstylus. Surstylus small, rounded, inner surface with many small, tubercle-like setae. Cercus large. Hypandrium broadly arched with strong terminal apodeme; inner lobe with short medial setae, broad, subquadrate with inner margin weak and confluent with small haired membrane; basal arms much reduced. Pregonite with narrowly rounded ventral lobe that has few short setae on inner surface, basally with longer, weaker, subquadrate lobe, posteromedial margin with extremely elongate, spinulose anterobasal process that curves anterodorsally to fuse with phallapodeme. Phallophorus wider at base, asymmetrical with left dorsolateral margin produced and fused to right sclerite of basiphallus. Both sclerites of basiphallus converging to base and with lateromedial membranous lobe that is larger on right side; apical third dark, weakly connected to basal section and abruptly directed inwards with apices perpendicular to long axis of phallus. Distiphallus of “ nigripes - type ” (capsule-shaped with subbasal crack-like slit for entry of ejaculatory duct, pronounced dorsobasal collar and medial convolution), with medial bend shallow and distiphallus nearly straight; distal section past this deviation slightly longer and wider than basal section, sides nearly subparallel in ventral view with abruptly widened base, with slight medial swelling and bulbous apical section that appears especially large and rounded in lateral view. Ejaculatory apodeme with short stem expanding into wide blade that is minutely striated and clear apically; stem and blade with dark medial rib; base very wide, strongly produced towards duct, distal side with long, thin, clear tubule; sperm sac large, clear.

Comments. Agromyza indistincta   is highly similar to other dark, grass-feeding congeners with a “ nigripes - type ” phallic structure, including A. parca Spencer   and A. pudica Spencer   (keying to couplet 31 in Spencer & Steyskal (1986)). These species have also been reared from Dichanthelium ( Eiseman & Lonsdale 2018)   and have only two well-developed dorsocentrals, and a minute apical tuft of hairs on the first flagellomere. Externally, A. indistincta   differs in that the apical tuft on the antenna is present in both sexes, the calypter hairs are dark brown in both sexes, the eye is 6.6–10.1 times higher than the gena (usually less than 5.0, but as large as 6.7 in some A. parca   ), and the apex of the fore femur is very narrowly light yellow. The basiphallus and distiphallus are most characteristic; the basiphallus is apically narrow, undivided, relatively dark and sharply angled inwards; the distal section of the distiphallus after the medial curve is angled along nearly the same plane as the basal section and not strongly deviated (i.e. the distiphallus is unusually straight), this distal section is only slightly longer but abruptly wider than the basal section, and the sides of the distal section are subparallel excluding a slight medial bulge and a unique apical chamber that is more strongly swollen dorsally. Another species reared from Dichanthelium   is A. proxima Spencer   ( Scheffer & Lonsdale 2018), but that species is more similar to other Agromyza   with a buckled, paler brown to orange frons and yellowish lunule.