Sciomyzidae

Can be distinguished from similar acalyptrate flies by the combination of: elongate antennae with pubescent arista; wings with or without conspicuous markings but with complete subcosta and closed anal cell; tibiae with dorsal preapical bristle; and absence of vibrissae. The family is most readily identified by association with marshy habitats and the distinctive predatory/parasitic larval biology on mollusks. Species-level identification requires examination of male genitalia and chaetotaxy; modern keys exist for regional faunas but comprehensive global keys are lacking.

Small to medium-sized flies, 2–14 mm in length, usually slender with predominantly dull grey, brown, reddish or yellow body coloration, rarely black-lustrous. Head semispherical or round. Antennae usually elongate with pubescent arista bearing shorter or longer hairs. Ocelli and ocellar bristles present (absent in Sepedon). Postvertical bristles divergent or parallel. One or two pairs of frontal bristles curve backward (lower pair sometimes curving inward). Interfrontal bristles absent; interfrontal setulae sometimes present. Vibrissae absent. Wings hyaline, often with dark spots or dark reticulate pattern; costa continuous, subcosta complete, crossvein BM-Cu present, anal cell (cell cup) closed. Tibiae almost always with dorsal preapical bristle.

Aquatic and semi-aquatic environments including edges of ponds, rivers, marshes, and drainage ditches. Adults found in marshy vegetation, woodland near water, and occasionally dry open habitats depending on larval requirements. Larval habitats range from fully aquatic to semi-aquatic to terrestrial, corresponding to the microhabitats of their mollusk prey.

Worldwide distribution across all biogeographic realms, but poorly represented in Australasian and Oceanian realms. Western Hemisphere: 274 species in 37 genera. Central and South America: 103 species in 25 genera. Documented from North America, Europe, Asia, Africa, and South America including specific records from Colombia, Brazil (Pantanal), China, Russia (Kuril Islands), and elsewhere.

Adults active during warmer months in temperate regions; some species overwinter as adults. One species (Sepedon) observed active in February in Colorado, suggesting early spring emergence in some regions.

Adults feed on dew and nectar. Larvae are predators or parasites of freshwater and terrestrial mollusks, primarily snails and slugs; some species attack snail eggs or fingernail clams. Larvae mainly prey on non-operculate snails. Some species with aquatic larvae are adapted to breathing underwater.

• Freshwater pulmonate snails - predator/parasitePrimary hosts for larval development
• Terrestrial slugs - predator/parasiteHosts for terrestrial larval species
• Fingernail clams (Sphaeriidae) - predatorOccasional prey for some species
• Snail eggs - predatorAttacked by occasional species

Females deposit small numbers of eggs in masses on emergent vegetation. Larvae develop through three instars as predators or parasites of mollusks; first and second instars require juvenile mollusks, third instar can take larger prey. Some terrestrial species have penultimate larval instar that emerges from host, with final instar predatory on multiple snails. Mature larvae pupate in capsule-like, boat-shaped puparium that floats amidst organic matter at water margins. Adults emerge from puparium; some species overwinter as adults.

Adults characteristically rest on vegetation head-downward. Males of some genera (e.g., Sepedon) have modified hind legs with bowed tibia and swollen, toothed femur for embracing females during courtship. Larvae are efficient predators, with individual larvae consuming 8–50 snails depending on species. Aquatic larvae suspend themselves just beneath water surface using water-resistant hairs surrounding posterior spiracles.

Significant predators and parasites of freshwater and terrestrial mollusk populations. Potential biological control agents for aquatic snails that serve as intermediate hosts of schistosomes and livestock liver flukes. Contribute to regulation of mollusk populations in wetland ecosystems. Serve as food source for other aquatic and terrestrial predators.

Investigated as potential biocontrol agents for medically important snails that transmit schistosomiasis and other parasitic diseases in tropical regions. Field trials have yielded mixed results. Of interest in forensic entomology and wetland ecosystem studies. No significant economic pest status; generally considered beneficial for mollusk population regulation.

• Neriidae (cactus flies)Both families have elongate bodies and long legs; distinguished by Sciomyzidae having arista pubescent (not apical on postpedicel as in Neriidae) and different habitat preferences
• MuscidaeSome superficial similarity in body form; distinguished by Sciomyzidae lacking vibrissae and having distinctive wing venation with closed anal cell
• Ephydridae (shore flies)Share aquatic/semi-aquatic habitats; distinguished by Sciomyzidae larval predation on mollusks versus Ephydridae algae-feeding or other diets

• Diptera
• acalyptrate
• marsh flies
• snail-killing flies
• mollusk predators
• wetland insects
• biocontrol
• aquatic insects

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• About | Entomology Research Museum
• Bug Eric: Snail-killing Flies, genus Sepedon
• Diptera | Beetles In The Bush | Page 7
• flies | Beetles In The Bush | Page 7
• FAMILY SCIOMYZIDAE
• Biology and Systematics of the Sciomyzidae
• Biology of Hedria mixta (Diptera: Sciomyzidae)1
• Biology of Snail-Killing Sciomyzidae Flies. By Lloyd Vernon Knutson and Jean-Claude Vala. Cambridge and New York: Cambridge University Press. $150.00. xix + 506 p. + 4 pl.; ill.; Index 1: subject; Index 2: genera and species cited other than Sciomyzidae, Phaeomyiidae, and Mollusca; Index 3: group names cited other than Sciomyzidae, Phaeomyiidae, and Mollusca; Index 4: suprageneric names in Sciomyzidae and Phaeomyiidae. ISBN: 978-0-521-86785-6. [A DVD is included.] 2011.
• BIOLOGY OF A SLUG-KILLING FLY, <italic>TETANOCERA ELATA</italic> (DIPTERA : SCIOMYZIDAE)
• First data on Sciomyzidae (Diptera) of Iturup Island (Kuril Islands)
• Sepedon (Diptera: Sciomyzidae) species from China, with notes on taxonomy and distribution
• On the Topologies of micro/macrohabitats in the Mollusca-Sciomyzidae Taxocene
• New distribution records for Sciomyzidae (Diptera) from the Pantanal, Brazil