Melanagromyza verbenivora 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 : 13-14

Melanagromyza verbenivora Eiseman & Lonsdale , spec. nov.

( Figs. 20–23 , 66–67 , 117–121 )

Holotype. USA. IOWA: Winneshiek Co., Beard Farm , 12.vii.2017, em. summer 2017, J. van der Linden, ex Verbena stricta , # CSE4648 , CNC1144043 (1♁).

Paratypes. IOWA: same data as holotype, # CSE4649 , CNC1135656 (1♀) ; same data as holotype, em. 14.vii.2017, # CSE4653 , CNC1144047 (1♁ [illustrated]) ; Winneshiek Co., Beard Farm , vi–vii.2017, em. summer 2017, J. van der Linden, ex Verbena stricta , # CSE4657 , CNC1144042 (1♀) ; Decorah, Trout Run Trail , 43°18’5.04”N 91°48’6.60”W, 12–22.vii.2017, em. late vii—early viii.2017, J. van der Linden, ex Verbena stricta , # CSE4942 , CNC1643670–1643672 (1♁ 2♀) .

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

Host. Verbenaceae : Verbena stricta Vent.

Larval biology. ( Figs. 66–67 ) Some larvae bore in the stem, forming a spiral gallery that is partly visible externally. This causes some stunting of the growing shoot and wilting of the terminal portion ( Fig. 66 ). Others bore in the rachis of more developed shoots, resulting in a somewhat thickened seedhead with a shriveled, blackened tip ( Fig. 67 ). The interior of the stem or rachis is filled with granular frass.

Puparium. ( Fig. 23 ) Whitish; formed within the larval feeding site.

Phenology and voltinism. Larvae feed in early summer, with adults emerging beginning in mid-July. Later generations have not been observed.

Distribution. USA: IA.

Adult description. Wing length 2.4–2.6 mm (♁), 2.7–2.9 mm (♀). Length of ultimate section of vein M 4 divided by penultimate section: 0.7. Eye height divided by gena height: 4.8–5.3. First flagellomere small, rounded. Lunule extending to level of middle ori. Ocellar triangle slightly shinier than vitta, extending to level of middle or posterior ori. Facial carina shallow, sharp. Gena shallowly upcurved anteriorly. Cheek narrow, only evident on anterior half. Clypeus rounded. Head (seen laterally) longest at midpoint. Eye tapering to a point posterodorsally. Thorax subshining.

Chaetotaxy: Three ori, two ors; spacing subequal with anterior ori sometimes slightly distant; setae becoming slightly more slender and short anteriorly. Ocellar and postvertical setae subequal to posterior ori. Eye sparsely short setose on dorsal half; female with hairs slightly denser dorsally, male with longer, denser patch of hairs dorsomedially. Orbital setulae in several scattered rows; erect to slightly reclinate. Two strong dorsocentral setae. Acrostichal setulae in ten irregular rows. Katepisternum with two additional smaller, closely spaced setae dorsomedially. Mid tibia with two posteromedial setae.

Coloration: ( Figs. 20–22 ) Setae dark brown. Body dark brown, including halter; thorax and abdomen metallic green with blue tint that is stronger on abdomen; blue color dominant in one female. Calypter margin and hairs yellow.

Genitalia: ( Figs. 117–121 ) Epandrium with small posteroventral spine. Surstylus fused to anteroventral margin of epandrium, very short and wide with 1–3 irregular rows of tubercle-like setae along inner surface. Cercus large, well-developed. Hypandrium subtriangular with apex slightly narrowed; inner lobe U-shaped and irregular with several sockets. Phallophorus (damaged in dissected male) tapering basally, venter bulging. Basiphallus U-shaped, nearly reaching mesophallus. Mesophallus cylindrical, slightly curved, narrowed to ventromedial point of fusion on distiphallus; base of mesophallus and distiphallus level. Distiphallus pear-shaped in ventral view, with narrow ventromedial plate swollen immediately past mesophallus; ventrolateral tubules narrow, largely hidden behind mesophallus along midline; dorsal chamber widest dorsally, broadly opened apically, with one pair of thick spinulose dorsal pads on inner surface; tubular inner process relatively wide, not far exceeding ventral plate. Ejaculatory apodeme not found.

Comments. The only previous record of a North American Melanagromyza from Verbena was that of an unemerged male of an apparently undescribed species that was said to be entirely black, extracted from a stem of V. scabra Vahl in Florida ( Spencer & Stegmaier 1973). It was noted that “The posterior spiracles of the puparium each bear ten bulbs, without a central horn; the two processes are separated by twice their own diameter.” Unfortunately no puparia of M. verbenivora have been preserved for comparison. Melanagromyza verbenae Spencer was described from adults caught on V. litoralis Kunth in Chile, and due to the general similarity of the male genitalia with those of the Florida specimen, Spencer (1982) considered it certain that this plant was the larval host and presumed that the Chilean species is likewise an internal stem borer. Spencer (1990) referred to the two species as “related or possibly identical”.

Using Spencer & Steyskal (1986), some specimens of Melanagromyza verbenivora key to M. longensis , which also has three ori and a similar phallus, but in that species, the arista appears bare (not minutely pubescent), there are about eight rows of acrostichal setulae, the basiphallus nearly forms a complete ring, and the dorsal chamber of the distiphallus is more rounded dorsally (not flat) and constricted apically (not broadly open). Other specimens will key to M. verbesinae , but in this species there are two ori, the ocellar triangle does not reach the posterior ori, and the distiphallus is widest apically. The gena is slightly angled forward as in M. buccalis Spencer , but not as prominent; M. buccalis is slightly smaller (wing length 1.9–2.5mm), there are two to four ori (widely spaced if only two), there are only eight rows of acrostichal setulae and the phallus is narrower.

Figures

FIGURES 13–23. Figures 13–15: Melanagromyza rudbeckiae Eiseman & Lonsdale, spec. nov.; 13: paratype, dorsal; 14: same, head; 15: same, lateral. Figures 16–19: M. urticae Eiseman & Lonsdale, spec. nov.; 16: holotype, dorsal; 17: same, head; 18: same, lateral; 19: puparia. Figures 20–23: M. verbenivora Eiseman & Lonsdale, spec. nov.; 20: holotype, dorsal; 21: same, head; 22: same, lateral; 23: puparium.

FIGURES 59–72. Mines and other feeding damage of Agromyzinae on host plants: 59: Agromyza aristata Malloch on Celtis laevigata; 60: Melanagromyza arnoglossi Eiseman & Lonsdale, spec. nov. on Arnoglossum sp.; 61: M. hieracii Eiseman & Lonsdale, spec. nov. on Hieracium scabrum; 62: M. minimoides Spencer on Rudbeckia lacinata; 63: same, section of flower head with puparia inside; 64: Ophiomyia abutilivora Spencer on Abutilon theophrasti; 65: same; 66: Melanagromyza verbenivora Eiseman & Lonsdale, spec. nov. on Verbena stricta, spiral gallery in stem with resulting leaf wilting; 67: same, affected seedhead; 68: Ophiomyia carolinensis Spencer on Symphyotrichum patens; 69: O. cf. frosti Spencer on Lactuca (puparium at upper right); 70: O. rugula Eiseman & Lonsdale, spec. nov. on Baccharis halimifolia; 71: same; 72: same, backlit, showing empty puparium.

FIGURES 117–121. Melanagromyza verbenivora Eiseman & Lonsdale, spec. nov., male genitalia; 117: external components, left lateral; 118: same, ventral; 119: hypandrium to epiphallus, ventral; 120: phallus, ventral; 121: same, left lateral.