Silba fungicola MacGowan, 2020

Macgowan, Iain, 2020, Two new species of Silba (Diptera; Lonchaeidae) from Japan with unusual larval development sites, Zootaxa 4755 (1), pp. 177-182 : 178-182

Silba fungicola MacGowan sp. nov.

Description. Male: Head: Eyes bare. Frons, sub-shining black, dulled by microsculpture, at narrowest point anterior to ocellar triangle approximately 0.5x eye width. Orbital plate sub-shining black, dulled by microsculpture, bare apart from orbital seta. Frontal and interfrontal setulae very short, approximately 0.1x length of orbital seta. Lunule setulose, ground colour black. Face and parafacials sub-shining black. Anterior genal setulae forming a single row of 3–4 along mouth margin, these slightly separated from the other genal setulae. Antennae entirely black, postpedicel length to depth ratio 2.7:1. Arista, plumosity short, at greatest extent 0.5x width of postpedicel.

Thorax: scutum grey dusted, sub-shining black, covered with setulae approximately 0.25x length of orbital seta. Anepisternum, grey dusted, anterior setae in a vertical row of 4, the ventral pair weaker than the dorsal, 3 posterior setae, shorter setulae scattered between these rows. Katepisternum grey dusted, 2 setae near dorsal margin, the posterior slightly stronger than anterior, a few setulae lying anterior to these along the anterior margin of the sclerite. Proepimeron and proepisternum each with 1 seta, that on the proepisternum much stronger than that on the proepimeron. Scutellum, grey dusted contrasting with the sub-shining black of the thoracic scutum, on margin with 3–4 setulae between lateral and apical setae, 2 very short setulae between apical setae. Calypteres whitish with a slightly brown margin, fringe white, of uniform length. Halteres black with a black stalk. Wings clear, veins light brown, wing length 3.75mm. Legs entirely black including ventral row of spicules on fore and hind basal tarsomeres.

Male terminalia: ( Figures 1–4 ): In lateral view epandrium slightly higher than wide, anteriorly with a semi-circular excavation, numerous long setulae on ventral and posterior surface. Cerci, rather rectangular, approximately 0.5x height of epandrium, bearing numerous short, stiff setulae on posterior and ventral surfaces. Surstyli projecting only slightly postero-ventrally beyond the shell of the epandrium as a rather flat, rounded lobe. In ventral view; surstyli with a marginal row of stiff setulae, a pair of setulae present at base of cerci. Pregonites finger-like, slightly narrowed apically, each with a single apical seta. Postgonites large and square-shaped, a group of setulae present on median posterior angle. Internal view; prensisetae small, forming a single curved row of 5 near posterior margin of surstyli, one seta positioned near base of each cercus. Inner surface of surstylus with a band of small posteriorly directed setae along outer margin, approximately twelve long, transverse creases positioned on centrally, medial these an area of small, rounded tubercles. Phallus with basal portion deep and rectangular in shape, bearing numerous small spicules, intromittent organ long, slender and, slightly curved.

Female; similar to male apart from the usual sexual differences Aculeus relatively narrow. Apical segment with a long pair of dorso-basal and ventro-apical setulae, these more than 0.5x length of apical segment

Type material: Holotype ♂. JAPAN, Nanao city, Ishikawa prefecture. Sample 524. 22. vii. 2012. Leg. N. Tuno. Reared from larvae found in Amanita spissacea Imai, 1933 (Amanitaceae) .

Paratypes: With the same data as the Holotype 2♂ 3 ♀. Kanazawa city, Ishikawa prefecture, Sample 477, 9.vii.2012, 2 ♂ 3 ♀, reared from larvae found in Amanita ibotengutake Oda et al, 2002 ( Amanitaceae ). Nomi city, Ishikawa prefecture, Sample 119, 12.vii.2012. 1♂ 4♀, reared from larvae found in Lactarius sp. ( Russulaceae ). All leg. N. Tuno. All specimens in National Museum of Scotland .

Etymology: The specific epithet refers to the larval substrate.

Differential diagnosis: This is a rather typical Silba species the key specific characters being the structures of the male genitalia, particularly the lateral creases on the inner surface of the surstyli and the structure of the phallus.

This species is obviously a fungal specialist with 110 individuals being recorded from 3 families and 15 species of fungi in Japan. The major family utilised was Amanitaceae with 47% of the rearing records with the genera Amanita , Tylopilus , Boletus , Lactarius , Leccinum and Russula also acting as hosts ( Tuno et al, 2019)

Silba mitsuii MacGowan sp. nov.

Description. Male: Head: Eyes bare. Frons, narrow approximately 0.4x width of eye, covered with heavy grey dusting. Orbital plate grey dusted, bare apart from orbital seta. Frontal and interfrontal setulae short, approximately 0.25x length of orbital seta. Lunule, ground colour black. Face and parafacials very lightly grey dusted. Anterior genal setulae forming a single row of 7 along mouth margin. Antennae entirely black, postpedicel length to depth ratio 2.5:1. Arista with short plumosity, at greatest extent 0.4x width of postpedicel

Thorax: scutum sub-shining black, covered with setulae approximately 0.5x length of orbital seta. Anepisternum, heavily grey dusted anteriorly, a vertical row of 3 anterior and 4 posterior setae on left side of thorax, 4 anterior and 3 posterior on right, a scattering of shorter setulae between these rows. Katepisternum grey dusted, 2 setae positioned near dorsal margin, the posterior slightly stronger than anterior, a few setulae lying anterior to these. Proepimeron and proepisternum each with 1 seta. Scutellum, more heavily dusted than thoracic scutum, margin with 7–8 setulae between lateral and apical setae, 4 between apical setae, all these setulae relatively long, approximately 0.5x length of lateral setae. Calypteres blackish with a dense fringe of black setulae. Halteres black with a black stalk. Wings slightly fumose anteriorly basally, veins dark brown Wing length 4.4mm. Legs entirely black including ventral row of spicules on fore and hind basal tarsomeres.

Male terminalia: ( Figures 7–10 ). In lateral view epandrium slightly wider than high, anteriorly with a semi-circular excavation, numerous long setulae located ventrally and posteriorly. Cerci, rather rectangular, approximately 0.5x height of epandrium, bearing numerous short, stiff setulae on posterior and ventral surfaces. Surstyli projecting postero-ventrally from the shell of the epandrium as a large slightly angular lobe. Ventral view; surstyli with a marginal row of stiff setulae, a single setula present at base of each cercus. Pregonites finger-like, slightly bifurcated apically, with a single apical seta. Postgonites small and simple, narrowed apically with a single apical seta. Internal view; prensisetae forming a single curved row of 6 near posterior margin, 1 seta lying anterior to this row and one near base of cerci, ventrally with a covering of numerous small spicule-like setulae. Phallus U-shaped, with a pair of long sinuous basal processes and large, broad, spiculate lateral processes, intromittent organ short, slightly curved.

Female: similar to male apart from the usual sexual differences. Frons width 0.5x eye width. Calypteres yellowish-white with a relatively dense fringe of white setulae. Wings clearer than in male with more yellowish veins.Aculeus relatively broad and strong, narrowing towards the blade-like apical segment which is slightly rounded apically. Apical segment ventrally with 3 pairs of lateral setulae, apical pair of the row 2x as long as the preceding pairs.

Type material: Holotype ♂. JAPAN, Tokyo. Hachioji , 18.iii.2015. leg H. Mitsui ex. flower buds of Camellia japonica L.

Paratypes: 6 ♂ 6 ♀ with the same data as the Holotype

The holotype and 4 ♂ 4 ♀ paratypes deposited the National Museum of Scotland, Edinburgh ( NMS). 2 ♂ 2 ♀ paratypes in the Laboratory of Systematic Entomology, Hokkaido University Museum ( SEHU).

Etymology: the specific epithet refers to Dr. Hideyuki Mitsui who first found this species developing in Camellia flower buds.

Differential diagnosis: This is a rather typical Silba species the key specific character being the distinctive structure of the phallus. The condition of having differently coloured calypters and fringes in the male and female is not unknown in Asian Silba species being found in species such as Silba capsicarum McAlpine, 1956 and Silba atratula (Walker, 1860) ( MacGowan & Rauf 2018) .

Although the presence of the larvae in the flower buds of C. japonica is likely to cause premature bud drop, lack of flowering and reduced seed production there would appear to be no recognised agricultural or horticultural impact. In Japan Camellia oil is produced from C. japonica , although amount is very small and it is also cultivated for horticultural use. Whether S. mitsuii or other Silba species attack other Camellia species is as yet unknown. There would be a potentially damaging agricultural impact if Silba larvae were to attack the buds of C. oleifera Abel, 1818 an important source of edible oil cultivated extensively in China. It is also possible that C. sinensis (L.) Kuntze (tea) could also be attacked by this species. Although no systematic study seems to have been carried out there are at present no reports of this or any related Silba species causing agricultural damage to C. japonica , C. oleifera or C. sinensis (M. Kimura pers.com.).

Figures

FIGURES 1–4. Silba fungicola sp. nov. 1.Epandrium and associated features lateral view. 2. Same, ventral view. 3. Surstylus, inner view. 4. Phallus, lateral view.

FIGURES 7–10. Silba mitsuii sp. nov. 7. Epandrium and associated features lateral view. 8. Same, ventral view. 9. Surstylus, inner view. 10. Phallus, lateral view.