Calocoenia Mathis, 1975

Mathis, Wayne N. & Sepúlveda, Luciane Marinoni and Tatiana A., 2025, Phylogeny and taxonomy of the shore-fly tribe Ephydrini with comments on related tribes in Ephydrinae (Diptera: Ephydridae), Zoologia (e 24044) 42, pp. 1-42 : 12-14

Calocoenia Mathis, 1975

Figs 10–15

Calocoenia Mathis 1975: 78 (feminine; as a subgenus of Paracoenia ; feminine; type species: Paracoenia platypelta Cresson 1935 , original designation). – Mathis 1980: 7 [revised status]. – Mathis and Zatwarnicki 1995: 235–236 [world catalog].

Diagnosis. Specimens of Calocoenia closely resemble those of Paracoenia but may be distinguished from the latter and other genera of Ephydrini by the following combination of character states: Generally dark colored.

Head: Mesofrons subshiny to shiny, inconspicuously setulose; 2 large, lateroclinate fronto-orbital setae; medial and lateral vertical setae both well developed; paravertical seta well developed, about half length of cruciate vertical seta. Arista pectinate, dorsally branching rays subequal to half the length of cruciate vertical seta; arista pectinate, dorsally branching rays subequal to half width of basal flagellomere. Face with interfoveal carina, but dorsal crease not as distinct as in specimens of Paracoenia . Eye subspherical to sub-elliptical, oriented at slight oblique angle to general plane of head.

Thorax: Acrostichal setulae uniformly small, in 2 rows that extend to base of scutellum; 5 (1+4) well-developed dorsocentral setae; postpronotum with 2–3 larger setae; postsutural supra-alar seta well developed, subequal to anterolateral postalar seta; scutellar disc almost flat; prosternum bare. Costal margin with evenly spaced spine-like setae distinct from remaining setae; R stem vein bare. Hindcoxa bare posteriorly along ventral margin; with dorsum subplanate; pulvilli well developed; tarsal claws short and distinctly curved.

Abdomen: Male tergite 5 slightly wider than long; tergites generally unicolorous. Male terminalia: Surstyli as angulate processes extended from ventral margin of epandrium, contiguous medially; aedeagus well developed, acutely pointed apically. Female abdomen: Female ventral receptacle with small operculum, conformation subtrapezoidal in lateral view, extended process much longer than width of operculum.

Distribution. See under each subgenus.

Remarks. Although first described as a subgenus within Paracoenia ( Mathis 1975) , this taxon was later accorded generic status, as it was recovered as the sister group to the combined Paracoenia / Thiomyia lineage and not as a lineage from within Paracoenia ( Mathis 1980: 7–8) .

Subgenus Calocoenia Mathis, 1975

Figs 13–15 Calocoenia Mathis 1975: 78 (feminine; as a subgenus of Paracoenia ; type species: Paracoenia platypelta Cresson 1935 , original designation). – Mathis 1980: 7 [revised status]. – Mathis and

Zatwarnicki 1995: 235 [world catalog].

Diagnosis. Although similar to Paracoenia s. str. and

Leptocoenia , Calocoenia may be distinguished from either as follows: Body length 3.4–4.0 mm; subshiny to shiny, metallic brown to greenish-brown; microtomentose, gray ventrally.

Head: Mesofrons shining, bronze-gold metallic reflections; pectinate branches of arista not more than twice aristal width at base; pruinose face tan; interfoveal hump not as prominent as Paracoenia s. str., dorsally sloping; eye large, subcircular, width in profile double the length of projecting face in profile; gena-to-eye ratio 0.25; width-to-height ratio 0.66; height-to-length ratio 0.90. Chaetotaxy of head and thorax like Paracoenia s. str. except acrostichal hairs.

Thorax: Acrostichal setulae in 2 rows; dorsum microtomentum to subshiny; 5 (1+4) well-developed dorsocentral setae; scutellum flattened; pleural areas concolorous with mesonotum centrally, becoming microtomentum, grayed marginally, halters yellow. Wings with costal setae on dorsal and ventral margins; costal vein ratio 0.20; M 1 vein ratio less than 0.80. Male midfemur without comb of setulae.

Abdomen: Generally uniform, concolorous; male tergites more noticeably narrowed apically; subshiny to shiny, brown metallic reflections; tergite 5 of male more or less truncate, without anteroventral process; sternite 5 with three posteriorly oriented prongs. Male terminalia: Symmetrical; epandrium subelliptical with closely fused surstyli ventrally and a medial groove; surstylus broadly attached to ventral margin of epandrium, approximate medially, shallowly bifurcate apically with small medial process and larger lateral process; aedeagus elongate, narrow, tapered to acutely pointed, curved apex; phallapodeme robustly crescent shaped in lateral view; gonite with apical half similar to apex of aedeagus in lateral view, tapered, curved, acutely pointed. Female abdomen: Female ventral receptacle with operculum wider than high, extended process considerably longer than operculum.

Distribution. Nearctic: Temperate western Nearctic Region from Alberta in Canada south through California and New Mexico.

Remarks. Calocoenia s. str. is a monotypic subgenus that only occurs in western North America within temperate zones. We know nothing about the natural history of this species or its immature stages.

Subgenus Leptocoenia Mathis, 1975

Figs 10–12

Leptocoenia Mathis 1975: 81 (feminine; type species: Coenia paurosoma Sturtevant and Wheeler 1954 , original designation). – Mathis and Zatwarnicki 1995: 236 [world catalog]. – Zatwarnicki and Kahanpää 2014: 344 [ Finland].

Diagnosis. Specimens of Leptocoenia closely resemble those of Calocoenia s. str. and Paracoenia but may be distinguished from the latter and other genera of Ephydrini by the following combination of character states: Moderately small shore flies, body length 2.1–2.6 mm; generally dark brown, microtomentose.

Head: Fronto-orbital areas, mesofrons nearly concolorous, the later subshiny; pectinate aristal branches at most 2.5X aristal width at base; interfoveal hump not prominent, without pronounced dorsal indentation; microtomentose face light tan; longest setae along ventral margin of face approximately 3/4 length of interfoveal hump height; genal seta weak, subequal to humeral setae. Gena-to-eye ratio 0.175; width-to-height ratio 1.00–0.65; height-to-length ratio 0.93; eye-width-to-face-length ratio 0.30.

Thorax: Mesonotum sparsely microtomentose; scutellum partially flat; acrostichal setae in two rows; 4 (1+3) well-developed dorsocentral setae; postpronotal setae present; halteres yellowish-brown to brown. Costal setae weak, developed only on dorsal margin; costal vein ratio 0.18–0.20; M 1 vein ratio 0.63–0.65. Posteroventral surface of midfemur not bearing a row of comb-like setae.

Abdomen: Ventral margin of male tergite 5 not produced as a lobe. Male terminalia: Surstylus well separated apically with a small medial triangular process between surstyli comparable to structure in Paracoenia s. str. (triangular process in Paracoenia s. str. better developed in comparison with surstyli); aedeagus generally L-shaped, robust, apically tapered to acute point; phallapodeme in lateral view hemispherical; gonite narrow, with a small, shallow, subapical projection, apex curved anteriorly, point- ed. Female abdomen: Female ventral receptacle with small operculum, helmet-like, extended process three times longer than opercular height.

Distribution. The only known species, C. paurosoma , has a disjunct Holarctic distribution, occurring in the western and temperate Nearctic Region (Alberta in Canada south through Wyoming and Colorado) but also in Finland and Sweden in the western Palearctic Region. We suggest that this distribution may be the result of sampling error, i.e., a lack of sampling of potential habitats between these vastly disjunct areas.

Remarks. Leptocoenia , like the subgenus Calocoenia , is a monotypic subgenus, and it too would be an excellent candidate for molecular analysis to respond better to questions such as: (1) Are the two disjunct areas genetically as well as morphologically related? (2) Is the current status of the subgenus within Calocoenia validated?

Figures

Figures 10–15. Calocoenia. Calocoenia paurosoma, (10) head anterior; (11) head lateral; (12) thorax dorsal. Calocoenia platypelta, (13) head anterior; (14) head lateral; (15) thorax dorsal.