Ophiomyia nabali 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 : 18-19

Ophiomyia nabali Eiseman & Lonsdale , spec. nov.

( Figs. 24–28 , 122–126 )

Holotype. USA. IOWA: Winneshiek Co., Decorah, Twin Springs Park , 24.viii.2017, em.?, J. van der Linden, ex Prenanthes alba , # CSE4667 , CNC1135652 (1♁).

Paratype. IOWA: Winneshiek Co., Decorah, Twin Springs Park , 19.x.2017, em. spring 2018, J. van der Linden, ex Prenanthes alba , # CSE4641 , CNC1144031 (1♁).

Other material examined. IOWA: Winneshiek Co., Decorah, Twin Springs Park , 10& 13.ix.2017, em. spring 2018, J. van der Linden, ex Prenanthes alba , # CSE4668 , CNC1144030 (1 empty puparium), same data as paratype, # CSE4641 , CNC1144032 (1 partial puparium) .

Etymology. The specific epithet refers to the host plant genus, Nabalus Cass.

Host. Asteraceae : Nabalus albus (L.) Hook.

Larval biology. The larva mines in the stem (CSE4641) or bores in the petiole (CSE4667, CSE4668). In the latter case, slight discoloration is evident externally, and in one instance (which first alerted us to this species’ exist- ence), the petiole was partially severed and scabbed over. One petiole gallery was observed to begin as a narrow mine extending ~ 2.5 cm into the leaf midrib. After opening the petiole to inspect this larva, it was successfully transferred to the midrib of a dandelion leaf ( Taraxacum officinale F.H.Wigg. ), where it fed for over a week before perishing. At one point its linear mine wandered into the leaf blade and then back into the midrib, but this species has otherwise been observed only to feed in the midrib, petiole, and stem of Nabalus .

Puparium. ( Figs. 27–28 ) Black; formed just beneath the petiole or stem epidermis, through which the anterior spiracles protrude.

Phenology and voltinism. Larvae have been found beginning in late August. Pupae overwinter, with adults emerging in spring.

Distribution. USA: IA.

Adult description. Female unknown, wings of male not expanded; specimens died soon after emergence and are undeveloped, with one in poor condition; one specimen represented by partial puparium in preserved host stem; costa presumably extending to M 1, wing length likely to be approximately 2.3–2.7 mm based on body size. Eye height divided by gena height: 5.3. First flagellomere small, rounded. Ocellar triangle reaching level of posterior ori. Face with pronounced ridge with medial bulb; bulb narrow, with very thin medial groove that continues onto lunule where it is bordered by shallow ridges. Gena produced, forming nearly 60° angle; apex narrower and slightly pronounced. Cheek developed. Clypeus very narrow and apically truncated with arms bowed. Thorax subshining.

Chaetotaxy: Two ori, two ors. Fasciculus developed, strongly upcurved on apical ¼ where hairs separate and appear frayed. Ocellar and postvertical setae subequal to ors. Two strong dorsocentral setae. Approximately ten rows of acrostichal setulae. Mid tibia with one small posteromedial seta.

Coloration: ( Figs. 24–26 ) Setae dark brown. Body dark brown, including halter. Calypter margin and hairs dark brown.

Genitalia: ( Figs. 122–126 ) Surstylus short, rounded, fused to distoventral margin of epandrium, with several irregular rows of tubercle-like setae on inner-distal surface. Hypandrium with long, laterally bulging arms; distal region subtriangular with pointed apex; inner lobe twisted, U-shaped with several sockets. Phallophorus narrow with swollen venter and strongly constricted base. Basiphallus mostly consisting of strong right-lateral band that reaches level of distiphallus; very short, weak, ill-defined left lateral band present; base truncated along margin of phallophorus. Mesophallus small, cylindrical, fused to ventromedial surface of distiphallus. Distal half of distiphallus relatively long and well-sclerotized with lateral texturing, narrowing apically to broadly rounded apex that is slightly upcurved; with thick ventral ridge along midline; with slightly swollen medial chamber at level of mesophallus that extends posterodorsally and is flared behind dorsal opening; widest at base, which is mostly clear except for scattering of minute sclerotized patches that concentrate ventrally. Ejaculatory apodeme not found.

Comments. We have found similar Ophiomyia mines and puparia in stems and peduncles of Nabalus trifoliolatus Cass. in MA, NH, and NY, possibly representing O. nabali . The only other Ophiomyia known from Nabalus is O. congregata (Malloch) , which has a fringe of peristomal hairs in the male and no fasciculus. Whereas O. nabali feeds exclusively in the stem, petiole, and leaf midrib, overwintering as a black puparium, O. congregata feeds partly as a leafminer, overwintering as an immature larva in the crown of the plant and forming a whitish puparium in the spring ( Eiseman & Lonsdale 2018).

The unfortunate state of preservation of known specimens of Ophiomyia nabali prevents the confident use of existing keys for identification, but the genal angle (60°), presumed wing length and groove along the facial keel key the holotype to O. lacertosa Spencer using Spencer & Steyskal (1986). The strongly bent fasciculus and unusual phallic morphology would eliminate this as a possibility, as they exclude the possibility of including the type in any other known species. The mesophallus is somewhat small and inserted far forward on the distiphallus, but it is the distiphallus itself that is most characteristic.

Figures

FIGURES 24–31. Figures 24–28: Ophiomyia nabali Eiseman & Lonsdale, spec. nov.; 24: holotype, dorsal; 25: same, head; 26: same, lateral; 27: puparium within host; 28: same, host epidermis peeled back. Figures 29–31: O. rugula Eiseman & Lonsdale, spec. nov.; 29: holotype, dorsal; 30: same, head; 31: same, lateral.

FIGURES 122–126. Ophiomyia nabali Eiseman & Lonsdale, spec. nov., male genitalia; 122: external components, left lateral; 123: same, ventral; 124: hypandrium to epiphallus, ventral; 125: phallus, ventral; 126: same, left lateral.