Phytoliriomyza arcus Kato, 2022

Kato, Makoto, Yamamori, Luna & Imada, Yume, 2022, Diversity underfoot of agromyzids (Agromyzidae, Diptera) mining thalli of liverworts and hornworts, ZooKeys 1133, pp. 1-164 : 1

8. Phytoliriomyza arcus Kato sp. nov.

Figs 14 , 15

Material examined.

Holotype: Japan: 1♂ (MK-AG-a411), Nippara, Okutama, Tokyo Pref. (35.8504°N, 139.0274°E, 650 m asl), 15-III-2016 (as larva on P. pterospermum ), emerged on 28-IV-2016, NSMT-I-Dip 31934. Paratypes: Japan: 1♂1♀ (MK-AG-a16, a458), same data as holotype, emerged on 4-5-V-2016, NSMT-I-Dip 31935, 31937; 1♀ (MK-AG-191), Akka, Iwaizumi, Iwate Pref., 5-V-2012 (as larva on P. pterospermum ), emerged on 13-V-2012, NSMT-I-Dip 31936; 1♀ (MK-AG-a316), Mt. Myogi, Tomioka, Gunma Pref., 10-V-2021 (as larva on P. pterospermum ), emerged on 16-V-2021, NSMT-I-Dip 31938; 1♀ (MK-AG-189), Todai-shiraiwa, Ina, Nagano Pref., 30-IV-2011 (as larva on P. pterospermum ), emerged on 28-V-2011, NSMT-I-Dip 31939.

Other material.

Japan: On Plagiochasma pterospermum : 4♂4♀, Akka, Iwaizumi, Iwate Pref., 5-V-2012 (as larva), emerged on 27-28-V-2012; 9♂9♀, Mt. Myogi, Tomioka, Gunma Pref., 10-V-2021 (as larva), emerged on 14-21-V-2021; 10♂12♀, Narahara, Ueno, Tano, Gunnma Pref., 18-IV-2021 (as larva), emerged on 15-25-V-2021; 2♂5♀, Mt. Kano, Kanna, Tano, Gunma Pref., 28-XI-2014 (as larva), emerged on 4-V-2015; 2♂1♀, Mt. Futago, Ogano, Chichibu-gun, Saitama Pref., 10-IX-2017 (as larva), emerged on 20-X-12-XI-2017; 1♂3♀, Kanna-gawa, Nakatsugawa, Chichibu, Saitama Pref., 16-X-2012 (as larva), emerged on 5-V-2012; 9♂11♀, Todai-shiraiwa, Ina, Nagano Pref., 12-V-2021 (as larva), emerged on 1-13-VI-2021.

On Plagiochasma appendiculatum : 5♂4♀, Mt. Myogi, Tomioka, Gunma Pref., 10-V-2021 (as larva), emerged on 15-29-V-2021.

Diagnosis.

A small species (wing length 1.3-1.6 mm) having subshiny brown scutum with yellow pattern extending from mid-posterior margin to scutellum, yellow 1st flagellomere, yellow maxillary palpus, yellow halteres, and yellow legs. Male epandrium inner-subdistally with hypertrophied, elongated, strongly curved arm bearing a dark tubercle-like seta. Larva mines the thallus of Plagiochasma pterospermum and P. appendiculatum .

Description.

Adult male (Fig. 14A-E ).

Head: Head light yellow, with ocellar tubercle brown, back of head dark brown (Fig. 14C ). Antenna porrect, first flagellomere, pedicel and scape brown. Arista subbasal, black pubescent. Clypeus, face, gena, parafacial and postgena yellow. Proboscis normal, yellow; yellow, cylindrical (Fig. 14C ). Chaetotaxy: Front orbitals three pairs; one ori directed inward; two ors directed upward (Fig. 14B ). Orbital setulae minute and erect, in a single row.

Thorax: Thorax subshiny. Scutum subshiny yellow, with a brown medial stripe on anterior 2/3, one pair of brown presutural patches, and a pair of wide postsutural brown bands adjoining with the presutural patches (Fig. 14D ). Mediotergite brown, and anatergite and katatergite yellow. Pleuron largely yellow, anepisternum and anepimeron with small brown patches, venters of katepisternum and meron brown (Fig. 14B ). Haltere gray. Calypter margin and hairs gray. Leg segments yellow; tibia and tarsus darker (Fig. 14A ). Chaetotaxy: Scutum with 1+3 dorsocentrals, shortened anteriorly. Acrostichal setulae six pairs in two rows (Fig. 14D ). Wing: Wing length 1.3 mm, costa reaching M1 (Fig. 14A ). Length of ultimate section of vein M4 divided by penultimate section 1.7-1.8.

Abdomen: Abdomen dorsally subshiny grayish yellow (Fig. 14E ). Genitalia: (Fig. 14G-K ) Epandrium dark brown, rounded apically; inner-lateral margin with an incomplete comb comprising two or three short tubercle-like setae; inner subdistal surface with basally thickened, remarkably elongated, strongly curved arm bearing a dark tubercle-like seta apically (Fig. 14G, H, K ). Surstylus protruding ventrally, tapering toward apex, setose apically, with one short tubercle-like seta on inner-basal surface (Fig. 14K ). Cercus narrow, setose. Subepandrial sclerite V-shaped in posterior view, with a pair of ventrally projected plate-like lobes with a spine medially (Fig. 14K ). Hypandrium slightly sclerotized along outer margin (Fig. 14G ). Postgonite bare, goose barnacle-shaped, and cleft apically (Fig. 14G ). Phallophorus with deep incision below, articulated with phallapodeme, fused to epiphallus (Fig. 14I ). Basiphallus with a H-shaped dorsal sclerite; anterior arms of which protruding ventrolaterally (Fig. 14G-I ). Hypophallus broad, membranous with microtrichia scattered dorsally, medially with a pair of short confronting sclerites (Fig. 14G-I ). Paraphalli wing-like, lightly sclerotized posteriorly; diverging, angled anteroventrally, joined basally on to the base of mesophallus. Mesophallus dark, cylindrical, widest subbasally, as long as distiphallus (Fig. 14G-I ). Distiphallus comprising one pair of stout tubules; basal half composed of lateral dark sclerites and weaker medial region; distal half cylindrical, composed of a pair of dorsally and laterally pigmented sclerites, widening toward apex, with truncated, flared apex (Fig. 14I ). Ejaculatory apodeme pale and fan-shaped with broad stalk; base wide to one side; sperm pump clear.

Female (Figs 14F , 15C ). Similar to male, but slightly larger (Fig. 14F ). Wing length 1.6 mm. Postabdomen: (Fig. 15A, B ) Oviscape dark brown, setigerous (Fig. 15A ). Tergite 10 trifurcate, laterally uniting narrow pleural sclerites (Fig. 14B ). Each cercus with two stout, apical, trichoid sensilla, 1/3 length of cercus (Fig. 14B ). Spermathecae semi-orbicular, with truncate proximal ends (Fig. 14A ).

Variation.

The yellow posterior patch on the scutum varied from distinct to obscure ones among localities and even among individuals in some localities.

Etymology.

The specific name (arcus = bow) refers to the bow-shaped tubercle-like seta on the male epandrium.

Japanese name.

Yumihari-tsubozenigoke-hamoguribae.

Host plant.

Plagiochasma pterospermum and P. appendiculatum ( Aytoniaceae ).

Mine.

Larvae construct linear-blotch mines in the thallus and pupate in the mines (Fig. 15D-F ).

Biological notes.

The habitats of this species are limestone outcrops in temperate deciduous forests, where the host liverworts grow (Fig. 15D ). Our rearing records suggest that this species is univoltine, and that adults emerge from overwintered pupae in spring.

Distribution.

Japan: Honshu (Fig. 16 ). Recorded only from limestone areas in Tohoku and Kanto districts.

Remarks.

This species resembles P. plagiochasmatos and P. falcata in having a pair of brown lateral bands and a light yellow mark on scutum; it is distinguished from them by the dark haltere (yellow in these species) and by the morphology of the tubercle-like seta on subdistal margin of the male epandrium (curved outward in P. arcus ; simple and short in P. plagiochasmatos ; elongated and sickle-like in P. falcata ).

Figures

Figure 14. Phytoliriomyza arcus sp. nov. A-E holotype male A habitus B lateral C frontal D dorsal E posterior F paratype female (MK-AG-a 16), dorsal G-K male genitalia (G at type locality H-K at Todai-shiraiwa) G, H whole genitalia, ventral I phallic complex, lateral J ejaculatory apodeme, lateral K epandrium, ventral.

Figure 15. Female morphology and larval / adult ecology of Phytoliriomyza arcus sp. nov. A, B female postabdomen A oviscape and spermatheca at Shiraizasu B tergite 10 at Mt. Myogi C live fly at Mt. Myogi D habitat at type locality E mined thallus of Plagiochasma pterospermum at Mt. Myogi F mined thalli at Todai-shiraiwa.

Figure 16. Locality records of three Phytoliriomyza species associated with Plagiochasma spp.: P. arcus, P. plagiochasmatos and P. calcicola.