36. Phytoliriomyza caerulescens Kato sp. nov.

Figs 68, 69

Material examined.

Holotype: Japan: 1♂ (MK-AG-a562), Ugan-zaki, Ishigaki-Is. Yaeyama, Okinawa Pref. (24.4479°N, 124.0826°E, 10 m asl), 7-XI-2021 (as larva on Riccia billardieri), emerged on 19-XI-2021, NSMT-I-Dip 32104. Paratypes: Japan: 1♀ (MK-AG-a558), same data as holotype, NSMT-I-Dip 32105; 1♂2♀ (MK-AG-a589, a559, a590), Komi, Iriomote-Is. Yaeyama, Okinawa Pref., 9-XI-2021 (as larva on Riccia billardieri), emerged on 17-XI-8-XII-2021, NSMT-I-Dip 32106-32108; 1♂ (MK-AG-a576), Urauchi, Iriomote-Is. Yaeyama, Okinawa Pref., 8-XI-2021 (as larva on Riccia huebeneriana), emerged on 25-XI-2021, NSMT-I-Dip 32109.

Other material.

Japan: On R. billardieri: 65♂70♀, same data as holotype, 7-XI-2021 (as larva), emerged on 19-XI-5-XII-2021; 85♂82♀, Komi, Iriomote-Is. Yaeyama, Okinawa Pref., 9-XI -2021 (as larva), emerged on 22-XI-811-XII-2021; 18♂25♀, Urauchi, Iriomote-Is. Yaeyama, Okinawa Pref., 9-XI -2021 (as larva), emerged on 22-XI-811-XII-2021.

On R. huebeneriana: 2♂3♀, Ugan-zaki, Ishigaki-Is. Yaeyama, Okinawa Pref. 7-XI-2021 (as larva), emerged on 22-24-XI-2021; 10♂4♀, Komi, Iriomote-Is. Yaeyama, Okinawa Pref., 9-XI-2021 (as larva), emerged on 16-29-XI-2021; 13♂10♀, Urauchi, Iriomote-Is. Yaeyama, Okinawa Pref., 9-XI-2021 (as larva), emerged on 27-XI-15-XII-2021.

Diagnosis.

A small species (wing length 1.1-1.3 mm) having a pruinose gray scutum and scutellum, brown 1st flagellomere, yellow maxillary palpus, gray halteres, and yellowish brown legs. Male scutum uniquely with a pair of bluish bands. Male epandrium inner-laterally with two strong tubercle-like setae, and with ventrally elongated surstylus. Distiphalli bilaterally asymmetrical and tapering toward apex. Larva mines the thallus of Riccia billardieri and R. huebeneriana .

Description.

Adult male (Fig. 68A-E).

Head: Head largely light yellow, with frons and ocellar tubercle pruinose brown, and back of head dark brown (Fig. 68C). Antenna porrect; first flagellomere, pedicel and scape brown (Fig. 68B). Arista subbasal, brown, pubescent. Face, gena, parafacial and postgena yellow. Proboscis normal, yellow; palpus light yellow, cylindrical (Fig. 68C). Chaetotaxy: Front orbitals three pairs; one ori directed inward; two ors directed upward (Fig. 68B). Orbital setulae minute and proclinate, in a single row.

Thorax: Thorax pruinose. Scutum and scutellum, bluish gray with a medial and a pair of lateral longitudinal obscure dark gray bands (Fig. 68D). Subscutellum brownish yellow except brown posterior half. Mediotergite dark brown, anatergite light yellow except ventral dark brown corner, and katatergite light yellow (Fig. 68E). Pleuron largely brownish yellow; anepisternum with brown patch along lower margin; anepimeron with a small spot on anterior ventral corner; katepisternum and meron with large brown patches on venter (Fig. 68B). Haltere gray with inner surface light yellow, with stalk light yellow. Calypter margin and hairs gray. Leg segments yellowish brown, subdistally and basally with dark patches; tibia and tarsus darker (Fig. 68A). Chaetotaxy: Scutum with 1+3 dorsocentrals, shortened anteriorly (Fig. 68D). Acrostichal seta three or four pairs in two irregular rows. Wing: Wing length 1.1 mm, costa reaching M1 (Fig. 68A). Length of ultimate section of vein M4 divided by penultimate section 1.8.

Abdomen: Abdomen dorsally subshiny brown, posterior margin of each tergite narrowly yellow; epandrium dark brown (Fig. 68E). Genitalia: (Fig. 68L-O) Epandrium rounded apically; inner-lateral surface with 2-3 sharp, dark tubercle-like setae (Fig. 68N). Surstylus large and ventrally extended, tapering toward apex, with a row of strong setae on ventral margin (Fig. 68N). Cercus narrow, setose. Subepandrial sclerite with a pair of pointed dorsal lobes converging together distally, with a pair of narrow lateral plate-like lobes protruding dorsally (Fig. 68N). Hypandrium thin, sclerotized along outer margin (Fig. 68L). Postgonite bare, goose barnacle-shaped, cleft apically (Fig. 68M). Phallophorus with shallow incision below, articulated with dark phallapodeme, fused to epiphallus (Fig. 68L). Basiphallus with a pale dorsal broad sclerite; as long as mesophallus + distiphallus (Fig. 68M). Hypophallus broad membranous; lateral margins darkly sclerotized (Fig. 68M). Paraphallus absent. Mesophallus dark, cylindrical; with a pair of narrow lateral sclerites. Distiphallus comprising one pair of dark bilaterally asymmetrical tubules; left one is S-shaped, longer and thicker than the right one, tapering toward apex; right tubule short, truncated (Fig. 68M). Ejaculatory apodeme pale brown and fan-shaped with broad stalk; base dark and wide to one side; sperm pump clear (Fig. 68O).

Female (Fig. 68F-K). Similar to male, but slightly larger and frons wider than male. Ground color of scutum is more bluish, and two bluish bands on scutum are more intense than those of male. Wing length 1.3 mm. Postabdomen: (Fig. 69A-C) Oviscape dark brown, setigerous (Fig. 69A). Tergite 10 trifurcate, laterally uniting narrow pleural sclerites (Fig. 69C). Each cercus with two stout, apical, trichoid sensilla, 1/2 length of cercus (Fig. 69A). Spermathecae semi-orbicular; with truncate proximal ends (Fig. 69B).

Immatures. (Fig. 69D-F, J-O) At 3rd instar, larval body yellow and cylindrical. Mandibles paired, fused, asymmetrical and strongly sclerotized, each with two teeth; left teeth larger than right ones (Fig. 69D-F). Mandibles confluent with short sclerotized hypopharyngeal sclerite, connecting to a pair of tentoropharyngeal sclerites; dorsal cornu broad and long, ventral cornu shorter, comprising two fused arms; upper arm darkly sclerotized only at basal part. Puparium internal, slender and brown (Fig. 69J-O).

Etymology.

The specific name (caerulescens = blue) refers to the bluish bands on the scutum, which are especially prominent in the female.

Japanese name.

Aosuji-hatakegoke-hamoguribae.

Host plants.

Riccia billardieri (Fig. 69I-M) and R. huebeneriana (Fig. 69N, O) ( Ricciaceae).

Mine.

(Fig. 69I-O) Larvae construct linear-blotch mines in the thallus, and pupate in the mines. Because the thalli of the host plants are small and thin, the larva sometimes relocates to a fresh thallus. In the mine of the thallus, sporangia are left intact (Fig. 69M).

Biological notes.

The two host liverwort species grow on levees of paddy fields in subtropical islands (Fig. 69G, H). Recent overuse of insecticides and herbicides and abandonment of rice cultivation in these islands has caused a drastic decrease of diverse paddy-field-dependent plants, and these liverworts and the liverwort-associated fly species are considered to be threatened. Larvae of P. caerulescens were found mining thalli of these liverwort species in early November and adults emerged from late November to December.

Distribution.

Japan: Ishigaki and Iriomote Islands (Fig. 65).

Remarks.

This species is unique in that the female has blue lateral bands on the scutum. It resembles P. iriomotensis, P. ugetsu, and P. phaeocerotis in having a wholly dark scutum and yellow maxillary palpi, but it is distinguished from them by the blueish scutum and by the shape of the surstylus of the male epandrium (well-sclerotized, prolonged, and tapering ahead in P. caerulescens; less-sclerotized, not prolonged, and curved inward in the other species).

Species associated with hornworts