Flower visitation by adult shore flies at an inland site in Florida

Florida Entomologist, Sept, 2008 by Mark Deyrup, Leif Deyrup

Shore flies (Ephydridae) are small acalypterates whose larvae are usually aquatic or semi-aquatic. Adult feeding habits are varied and known for only a small proportion of species. Most adults consume algae or bacterial slurries, but some are predators on smaller arthropods, scavengers, or nectar feeders (Wirth et al. 1987). At the Archbold Biological Station in south-central Florida some adult ephydrids occur regularly on flowers. These species and their floral hosts are listed below.

The Archbold Biological Station (ABS), located in Highlands County, is near the south end of the Lake Wales Ridge, a distinctive sandy upland. During the rainy season (Jun-Oct) low areas on the Ridge accumulate water in extensive shallow ponds, more than 150 of which occur on the ABS. These ponds usually dry up in winter and spring. Their drying shores become zones of biological hyperactivity as oxygen becomes more available for plants and animals, stranded aquatic organisms die, algae become concentrated, and nutrients are released. Such edges are ideal for a variety of shore flies. Drying ditches and a permanent lake also produce ephydrids. About 45 species of ephydrids are known from the ABS, but there are probably many additional species. Only a small number of species are known to visit flowers at the ABS.

Specimens were collected with nets and aspirators from open flowers over a period of about 20 years. Over 150 species of plants were examined, of which only a small proportion attracted ephydrids. Only 1 or 2 representative specimens of each species were mounted from flowers of a single species of plant on a single day. These specimens are in the collection of the Archbold Biological Station. Most specimens were identified by the senior author, using taxonomic guides and ABS reference specimens identified by Willis Wirth, Wayne Mathis, and J. R. Vockeroth, all of whom examined the ABS ephydrid collection. Plants were identified by the senior author.

Annotated List of Flower-visiting Ephydridae at the ABS

Genus Allotrichoma. Some species of Allotrichoma, including the species listed below, were originally placed in the genus Pseudohecamede (Wirth et al. 1987). In a study of ephydrids of muddy shores, Thier & Foote (1980) found Allotrichoma sp. breeding in muskrat dung and dead snails. They suggest that larvae of this genus are scavengers.

Allotrichoma abdominalis (Williston). Many adults were seen on a scat or pellet of insect fragments in a wet flatwoods at the ABS; this species is probably a scavenger like the species studied by Thier & Foote (1980). If this species breeds in the corpses of stranded aquatic organisms, the seasonal ponds at the ABS are excellent habitats, as these ponds are on sandy substrates and often dry up rapidly at the end of the rainy season. Allotrichoma abdominalis belongs to a species group characterized by an elongate, pointed proboscis (Cresson 1942) that might be an adaptation for nectar feeding. The proboscis is superficially similar to that of 0lcella species (Chloropidae), which often occur on flowers together with A. abdominalis. Most flower records are from plants near wet areas, but a few are from sites 0.5 km or more from wet areas. ABS records: Feb-Mar, May-Jun., Aug-Dec. General distribution: Atlantic and Gulf States, California, Neotropics (Wirth 1965).

Genus Ceropsilopa. The biology of Ceropsilopa species is apparently unknown. Two species occur in salt marshes in Florida (Rey & McCoy 1986).

Ceropsilopa adjuncta Cresson. This species has been collected at the ABS in the vicinity of ditches and also in dry scrub some distance from water. It visits a variety of flowers as well as the extra-floral nectaries of Crotalaria pallida Ait. ABS records: Feb-May, Aug, Oct-Nov. General distribution: Florida, Puerto Rico (Wirth 1965).

Ceropsilopa coquilletti Cresson. ABS records: Apr, Aug. General distribution: southern U.S., Neotropics (Wirth 1965).

Genus Discocerina. Members of this genus, like many other ephydrids, are usually found on muddy shores, where they feed on accumulations of microorganisms and finely particulate debris (Foote 1995).

Discocerina obscura Williston. At the ABS adults were collected from the muddy shore of a seasonal pond. ABS records: Jan, Mar-Apr, Nov. General distribution: New York through Florida, west into Texas, south through the Neotropics (Wirth 1965).

Discocerina obscurella (Fallen). At the ABS common along muddy shores of seasonal ponds; also found around rotten oranges on a wet lawn. Elsewhere, this widespread species occurs in a great variety of habitats, including dry, sandy areas, grassy depressions, and various types of muddy shore habitats (Deonier 2002). ABS records: Jan-Apr, Aug-Dec. General distribution: Europe, North America, Neotropics (Wirth 1965).

Genus Hydrochasma. Members of this genus are associated with both inland and coastal marshes; H. leucoproctum (Loew) occurs in freshwater habitats (Thier & Foote 1980; Deonier 2002), and H. buccatum (Cresson) occurs along beaches and coastal marshes (Deonier 2002).