Paracoenia Cresson, 1935

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 : 27

Paracoenia Cresson, 1935

Figs 67–74

Paracoenia Cresson 1935: 356 (feminine; type species: Coenia bisetosa Coquillett 1902 , original designation). – Wirth 1965: 755– 756 [Nearctic catalog]. – Mathis 1975: 65–85 [revision of Nearctic species]. – Zack 1983a: 487–497 [biology and immature stages of P. bisetosa ]. – Mathis and Zatwarnicki 1995: 250–252 [world catalog]. – Yakovleva et al. 2024: 360–375 [biology and immature stages of P. fumosa ].

Diagnosis. Paracoenia is distinguished from other genera of the tribe Ephydrini by the following combination of characters: Small to large shore flies, body length 2.10–4.40 mm; dark colored and often with subshiny, metallic reflections.

Head: Face projected, transversely arched; paravertical setae large, subequal to vertical setae. Two well-developed lateroclinate fronto-orbital setae.

Thorax: Postpronotal seta distinct, length at least 1/2 as long as posterior notopleural seta; dorsocentral setae 5 (1+4); scutellum with dorsum convex; prosternum bare. R stem vein bearing 1–2 setulae above, inserted beyond transverse septum; costal vein ratio 0.19–0.27; M 1 vein ratio 0.81–0.92. Hindcoxa with row of setae posteriorly along ventral margin; tarsal claws short and distinctly curved, comparatively short; pulvilli well developed.

Abdomen: Male terminalia: Surstyli distinct as elongate, narrow, arm-like projections, projections oriented ventrally; a medial, triangular process between surstylar arms; gonite (sometimes called hypandrial process) well developed, sheathing aedeagus.

Third-Instar larva: Body length 9.50–18.80 mm; body fusiform, integument translucid; 12 segmented; 3-segmented antenna; maxillary (terminal) sensory organs (consisting of seven sensillae, separated by flattened ridges in 2 groups, 2 + 5); 3 legless thoracic segments, 1 st thoracic segment with two anterior spiracles; eight legless abdominal segments; caudal segment with anus ventrally, elongated as a long retractile, branched respiratory tube, tube length 30–50% body length.

Natural history: A few species of this genus occur in the effluent of hot springs, and some are uniquely found only at these sites. Moreover, some of the springs are sulfurous and otherwise inimical to most other forms of life. These species are as follows: P. calida Mathis from Wilbur Hot Springs (39°2.3’N, 122°25.3’W) in Colusa County, California; P. quatei (Wirth) from Sulphur Mountain Spring (34°25.7’N, 119°05.6’W) in Ventura County, California; P. beckeri (Kuntze) from Acque Albule (41 ° 54.2’N, 12°29.8’E), a sulfurous spring near Tivoli, Roma, Italy. Adults and immature stages of these three species were collected only at these respective and specific sites despite efforts to sample them from nearby habitats and elsewhere ( Wirth 1954 for P. quatei ; Giordani Soika 1956a for P. beckeri ; and Mathis 1975 for P. calida ). Wirth (1954) described the 3 rd- instar larva of P. quatei , which has small pseudopods along the ventral surface of segments, and these lack the long crochet-like setae, found more typically in larvae of Ephydra ( Aldrich 1912) .

A fourth possible species that may occur in hot springs is P. ampla Mathis , which is only known from Los Angeles , Los Angeles County, California. M.C. VanDuzee collected the holotype male in April of 1915. We wonder if the specific site were a hot spring, such as Alvarado Hot Springs, and if more specimens could be found there or at another hot springs in the area .

These species were perhaps preadapted to live in association with hot springs, as other congeners, such as P. wirthi Mathis (Tecopa Hot Springs) and P. turbida (Curran) (Yellowstone hot springs) have been collected in and on the effluent of some hot springs in addition to occurring in cold-water wetlands. The “preadaption” may involve the algal food source that lives in these hot springs and other aquatic sources.

Remarks. The lineage comprising Paracoenia and related genera in our data and analysis the sister group to the remaining taxa of Ephydrini . This lineage plus the remaining taxa of Ephydrini , as here delimited, is characterized by the following character states (some have become modified secondarily): 1. Number of dorsocentral setae: Although other genera of the subfamily Ephydrinae sometimes have five pairs of dorsocentral setae (e.g. Notiocoenia Mathis and Austrocoenia Wirth ), the anterior pair (or pairs) is weakly developed. There are five well-developed pairs only in members of Ephydrini (the anterior pair is presutural; specimens of Cirrula gigantea have the anterior four pairs of dorsocentral setae are weakly developed, a condition we interpret to be secondary). 2. Development of intrapostalar seta: In most species of the family, the intrapostalar seta is either lacking or is very much reduced, less than one-half the length of the postalar seta. In members of this lineage, the intrapostalar seta is frequently as long. 3. Setal vestiture of proepisternum: Throughout most of the family the proepisternum is bare of setae (although frequently it is thinly to densely microtomentose). In members of this lineage, there are numerous setulae that are generally conspicuously evident.

Figures

Figures 67–86. Paracoenia, Paraephydra and Setacera. Paracoenia wirthi, (67) head anterior; (68) head lateral; (69) thorax dorsal; (70) epandrium and surstyli posterior; (71) epandrium and surstyli lateral; (72) male 5th tergite lateral; (73) male 5th sternite ventral; (74) female ventral receptacle lateral. Paraephydra freitasi, (75) head anterolateral; (76) thorax dorsal; (77) epandrium and cerci posterior; (78) internal structures of male terminalia lateral; (79) surstylus lateral; (80) gonite lateral; (81) female ventral receptacle lateral. Setacera trichoscelis, (82) head anterolateral; (83) thorax dorsal; (84) internal structures of male terminalia lateral; (85) male terminalia lateral; (86) fused surstyli posterior.