Limnellia Malloch, 1925

Costa, Daniel N. R., Mathis, Wayne N., Marinoni, Luciane & Sepúlveda, Tatiana A., 2024, Phylogeny and taxonomy of the shore-fly tribe Scatellini (Diptera: Ephydridae: Ephydrinae), Zoologia (e 23100) 41, pp. 1-35 : 17-18

Limnellia Malloch, 1925

Figs 10 , 68–77

Limnellia Malloch 1925: 331 (feminine). Type species: Limnellia maculipennis Malloch 1925 , original designation. – Andersson 1971: 53–59 [review, European species]. –Mathis 1978: 250– 293 [revision of Nearctic species]. – Mathis and Zatwarnicki 1995: 258–261 [world catalog]. – Zhang and Yang 2009: 558–64 [review, Chinese fauna]. – Krivosheina 2012: 1–7 [review, Russian species]. – Mathis et al. 2014: 563–564 [review, Brazilian species].

Eustigoptera Cresson 1930: 126 (feminine). Type species: Notiphila quadrata Fallén 1813 , original designation. – Cresson 1935: 362 [objective synonymy and as stated].

Stictoscatella Collin 1930: 133 (feminine). Type species: Notiphila quadrata Fallén 1813 , original designation. – Cresson 1935: 362 [objective synonymy and as stated].

Stranditella Duda 1942: 30 (as a subgenus of Lamproscatella ; feminine). Type species: Notiphila quadrata Fallén 1813 , original designation. – Dahl 1959: 126 [objective synonymy and as stated].

Diagnosis. Limnellia is distinguished from other genera of the tribe Scatellini by the following combination of characters: mesonotum distinctly bi- or tricolored; wing infuscate, darker toward anterior margin, lighter toward posterior margin; and a large posterodorsal arm and gonal arch. Other characters useful to diagnose Limnellia species, include: 1 pair of well-developed, lateroclinate fronto-orbital seta; gena small (gena to eye ratio <0.21); mesonotum usually conspicuously multicolored with pattern of bands and/or spots.

Description: Minute to moderately small shore flies, body length 1.00–2.50 mm; mostly dark brown to black, microtomentose to bare, shiny, frequently with cinereous guttate and vittate maculae; species macropterous or brachypterous.

Head ( Fig. 10 ): Frontal vitta distinct from duller parafrons, subshiny; lateroclinate fronto-orbital seta 1 (rarely 2); medial and lateral vertical setae both well developed; ocelli arranged in isosceles triangle or absent. Antenna dark, arista at most macropubescent. Interfoveal dorsal hump of face low, face with shallow antennal grooves; facial setae mostly small, 1–2 lateral facial setae curved laterodorsally. Eye nearly round. Gena relatively short (gena to eye ratio <0.21), bearing 1 well-developed seta.

Thorax: Mesonotum usually conspicuously multicolored with pattern of bands and/or spots. Pleural areas usually dark brown with cinereous areas. Acrostichal setae uniform in size, small, arranged in 2 rows that extend to base of scutellum; dorsocentral setae 2 (0+2); supra-alar seta either reduced or lacking; disc of scutellum bare; lateral scutellar setae 2, basal pair one-third length of posterior pair. Legs typical, without distinct setae; color of tarsi variable but usually paler than tibiae; tarsal claws conspicuously curved and puvilli present below each claw. Wing strongly infuscate, darker on anterior margin and lighter on posterior margin, with several white spots in all cells; costa relatively long, extended to vein M 1; crossvein r-m distinctly distal to subcostal break; maculation pattern variable but generally recognizable for each species. Wing brachypterous to micropterous in a few species.

Abdomen: Tergites black, becoming shiny and polished posteriorly. Male terminalia ( Figs 68–77 ): sternite 5 present, sternite 6 absent. Epandrium a closed plate around cercal cavity, bearing articulated surstyli on anterior margin; surstylus as 2 plates or fused; gonites broadly Y-shaped, with broad base, bearing setae on ventral portion; aedeagus in lateral view shoe-shaped, without distiphallus; phallapodeme dorsoventrally flattened, usually with 2 lateral projections, rod-like, lacking a keel; ejaculatory apodeme lacking. Female terminalia: sternite 8 divided, as 2 lateral, subquadrate sclerites; female cerci without prominent setae. Female ventral receptacle without operculum, only extended process present.

Distribution. Widespread: Afrotropical, Australasian, Nearctic, Neotropical, Oriental (Chinese-Palearctic-Oriental transition), Palearctic Regions.

Remarks. Limnellia Malloch is an easily recognized genus within Scatellini because of the conspicuously multicolored mesonotum with patterns of bands and/or spots and the infuscate wing with several to numerous white spots. There is also a single lateroclinate fronto-orbital seta. Twenty-four species are known in the genus, mostly from the Nearctic Region (10 species). Nothing is known about the immature stages, behavior, or habitat preferences of this genus. Mathis (1978) presented a phylogeny of Nearctic species. Herein and following the precedent of previous papers (Mathis 1978, Mathis and Zatwarnicki 1995), Limnellia was recovered as the sister-group of Scatophila .

Four species of Limnellia from Neotropical, Palearctic and Australasian Regions demonstrate varying levels of brachyptery ( Hollmann-Schirrmacher and Zatwarnicki 1995, Mathis et al. 2004, Costa et al. 2016). Limnellia helmuti Hollmann-Schirrmacher and Zatwarnicki has a short and broad wing, and L. abbreviata , has a narrow wing. Neither species is capable of flight.

More recently, Costa et al. (2016) described two brachypterous species ( L. flavifrontis and L. vounitis ) from the Paramo of Venezuela and suggested that the brachyptery of these two species evolved independent of other congeners within Limnellia . These two species also have several modifications that are apparently related to their brachyptery, such as a compact thorax and reduced size of the halteres. There is also the complete loss of ocelli and ocellar setae as well as the first abdominal tergite. These features are synapomorphies that are unique to these two species. According to the collector of the two Venezuelan species, specimens were found in rotting wood or in leaf litter at high elevations, which are typical niches for brachypterous species ( Hackman 1964).

Figures

Figures 10–23. Head, wing and legs characters: (10) Limnellia sp., head anterior; (11) Scatella (Scatella) sp., head anteri- or; (12) Scatella (Parascatella) sp., head anterior; (13) Hyadina sp., head lateral; (14) Scatella (Parascatella) pilifera, head anterior; (15) Scatella (Scatella) stagnalis, mouth parts; (16) Philotelma sp., head lateral; (17) Physemops nemorosus, head anterior; (18)Ephydra riparia, mouth parts; (19) Scatophila caviceps, wing; (20) Scatella (Scatella) stagnalis, wing; 21, Dagus rostratus, wing; (22) Scatophila mesogramma, male, mid femur posteroventral; (23) Scatella (Scatella) stagnalis, male, fore femur anteroventral.

Figures 63-85. Male terminalia: (63–65) Notiocoenia acutella; (66–67) Halmopota mediterranea; (68–70)Limnellia huachuca; (71–73) Limnellia itatiaia; (74-77) Philotelma nigripenne; (78–81) Philotelma rossii; (82–83) Scatella (Synhoplos) neglectus; (84–85) Lamproscatella occidentalis.