First Record of the Marsh Fly Genus Ditaeniella (Diptera: Sciomyzidae) from Korea

Abstract

Members of this family Sciomyzidae are known as marsh flies and snail-killing flies because most of the known larvae are obligate predators of Mollusca, especially freshwater and terrestrial Gastropoda. Most species are found in the shallow ephemeral aquatic habitats with rich organic substrates, such as the hard-water streams, small ponds and lakes in mountain valleys. To date, a total of 8 marsh fly species in 4 genera have been known in Korea. During a taxonomic survey of the family Sciomyzidae in Korea, the authors have found the genus Ditaeniella Sack, 1939; thus, it was discovered for the first time in Korea. This genus can be distinguished by the other related taxa with hairs over much of the mesopleuri, hairs on the prosternum and one orbital seta. In addition, the nominate species, Ditaeniella grisescens Meigen, 1830 was also firstly recoded in the Korean fauna.

INTRODUCTION

The family Sciomyzidae has more than 540 species comprising 61 genera across the world’s biogeographical regions (Rozkošný, 1995; Elberg et al., 2009). Members of this family are known as marsh flies and snail-killing flies because most of the known larvae are obligate predators of Mollusca, especially freshwater and terrestrial Gastropoda. The marsh fly habitat consists of hard-water streams, small ponds, lakes in mountain valleys, and they also thrive in shallow ephemeral aquatic habitats with rich organic substrates(Knutson and Vala, 2011).

Until now, 4 species of the genus Ditaeniella have been known in world. Of that, 2 species, D. parallela (Walker, 1852) and D. trivittata (Cresson, 1920) are recorded in Nearctic region. And D. patagonesis (Macquart, 1851) is only recorded in Neotropical region. Also, only one species, D. grisescens (Meigen, 1830) is known to be occurred in Palaearctic region (Knutson and Vala, 2011).

The family Sciomyzidae is very poorly studied and documented in the Korean peninsula. The first record of this genus from Korea was given by Steyskal (1951), who described a new species, Tetanocera chosenica, from Seoul. Subsequently, Steyskal (1956) also described a new species, Pherbellia ditoma, from Andong. Park (1967) recorded Sepedon aenescens Wiedemann that was misidentified as S. sphegea (Fabricius). Knutson (1977) mentioned Pherbellia nana reticulata (Thomson). Rozkošný and Kozánek (1989) described a new species, Pherbellia koreana, from North Korea, with a newly record species in the Korean fauna, Sepedon noteoi Steyskal misidentified as S. spinipes (Scopoli). Rozkošný et al.(2010) added two species to the Korean fauna, Colobaea eos Rozkosny and Tetanocera elata (Fabricius), while reviewing the Korean Sciomyzidae. Until now, eight species in four genera were known to occur in the Korean fauna.

During a taxonomic survey on the family Sciomyzidae in Korea, the authors found an additional genus, Ditaeniella Sack, 1939, along with the nominate species, Ditaeniella grisescens (Meigen, 1830), to be added to the inventory of Korean fauna.

The specimens examined in the present classification were based on the collections from several domestic localities throughout Korea, which were deposited in the School of Applied Biosciences, Kyungpook National University, Daegu, Korea.

SYSTEMATICS ACCOUNTS

Order Diptera Linnaeus, 1758

Family Sciomyzidae Fallen, 1820

Genus Ditaeniella Sack, 1939

Ditaeniella Sack, 1939: 37. Type species: Sciomyza grisescens Meigen, 1830.

Diagnosis. Frons mainly matt; mid-frontal stripe elongated and tapered anteriorly; only one orbital seta present; propleural seta distinct; prosternum haired; mesopleuron covered with distinct hairs; inner posterior margin of hind coxa with several hairs; anal vein on wing reaching posterior wing margin (Sack, 1939).

Ditaeniella grisescens(Meigen, 1830)(Fig. 1)

Sciomyza grisescens Meigen, 1830: 20. Type-locality: Versailles in France.

Pherbellia grisescens: Rivosecchi and Santagata, 1979: 473.

Ditaeniella grisescens: Rozkošný, 1987: 19.

Fig. 1. Ditaeniella grisescens. A, Male, lateral view; B, Female, lateral view; C, Male head, lateral view; D, Female head, lateral view; E, Male gonostyli. Scale bars: A, B=1 mm, C, D=0.5 mm, E=0.01 mm.

Diagnosis. Male: Head: curved in lateral view; cheeks broad; arista short-pubescent; 3rd antennal segment darkened in apical half; one orbital seta present (Fig. 1C). Thorax: mainly yellow to yellowish-grey and matt; mesonotum with darker stripes; one propleural seta; prosternum with a few haired; scutellum with two pairs of setae; 2 anepimeral setae. Legs: yellowish brown and grey; tarsus mainly dark; fore femur has dark stripes and one anterior seta; front femur 6 dorsal setae; fore tibia with one preapical seta; mid tibia several setae on edge; hind tibia one posterior seta (Fig. 1A). Wing: slightly infuscate without pattern; R4+5 and M1+2 parallel; anal vein reaching posterior wing margin; posterior cross-veins cloudy and almost straight (Fig. 1A). Abdomen: yellowish-grey; gonostyli postgonites develop and have spines; 5th tergite asymmetry (Fig. 1E).

Female: Entirely similar to male, but more darken; body mainly brown to brownish-grey (Fig. 1B, D).

Body Length: Male, 3.9-4.2 mm; female: 4.1-4.3 mm.

Wing Length: Male, 3.7-4.2 mm; female: 3.7-4.1 mm.

Specimen examined. Korea: 1♂, Gyeongsangbuk-do: Gunwi-gun, Hyoryeong-myeon, Hwagye-ri, 11 Jul 2017, Suh SJ; 2♂♂, Jeju-si: Yongdam-dong, Hancheon-gyo, 12 Jul 2018, Suh SJ; 1♂, 1♀, Gangwon-do: Samcheok-si, Osipcheon, 15 Sep 2018, Suh SJ; 3♀♀, Samcheok-si, Seongnam-dong, 25 Jun 2018, Suh SJ; 2♀♀, Yangyang-gun, Ganghyeon-myeon, 8 Jul 2016, Suh SJ; 1♂, 4♀♀, Jeollabuk-do: Gochang-gun, Heungdeok-myeon, 19 Oct 2018, Suh SJ.

Distribution. Korea (new record), Japan, China, Mongolia, Russia, Egypt, Turkey, Cyprus, Israel, Lebanon, Iran, Afghanistan, Europe.

Remarks. This species has asymmetry 5th tergite with the right side larger than the left. They have over half darken third antennal segment and body color darker in female than male. The genus Ditaeniella has been recorded only one species D. grisescens in Palaearctic region.