Flower Flies, or hover Flies, if you are English, are conspicuous members
of terrestrial ecosystems. Their size ranges from 4 mm to over 25 mm and
their coloration from bright yellow or orange to dull dark black or gray
with a few iridescent forms. Flower Flies are abundant on flowers, which
are used as mating sites and energy sources. Only the microdontines are
not found associated with flowers, but rather with their ant hosts. Many
flower Flies are Batesian mimices of stinging wasps and bees (Hymenoptera).
The economic importance of flower Flies is great. These Flies are pollinators of major significance. In some agroecosystems, such as orchards, they out perform native bees in pollinating the fruits. Syrphine maggots are important predators of pests, such as aphids, scales, thrips, and catepillars, and are rivaled only by lady-bird beetles and lacewings as predators useful for biological control. Some flower Flies, however, are detrimental. Maggots of a few species (Eumerus, Merodon) attack bulbs and tubers of ornamentals and vegetables. And a few species have been recorded as causing accidental myiasis in man.
Flower Flies are abundant everywhere except in arid areas of the Old World and in the extreme southern latitudes, Although flower Flies range to the highest latitudes in the north, they are absent from subantararctic islands and Antarctia.
Immature stages (eggs, maggots & puparia) are found in a diverse array of habitats. Larvae of the subfamily Microdontinae are inquilines in ants' nests. Those of Syrphinae are predaceous on soft-bodied arthropods, although some may occassionally be scavangers. Those of Eristalinae can predaceous (pipizines), saprophagous in litter and dead wood (most milesiines), coprophagous (some rhingiines and milesiines), mycetophagous (some rhingiines), phytophagous (as borers in tubers, stems, and wood, miners in leaves; most rhingiines, merodontines and some brachyopines), aquatic filter feeders (the rat-tailed maggots, mainly eristalines, some brachyopines and milesiines) or inquilines in social insect nests of termites, wasps, and bees (some volucellines and merodontines).
The family Syrphidae is broken down into 3 subfamily and 15 tribes and contains more than 6,000 described species. Total number of species is much greater, for example, more 200 species are known from Costa Rica but not yet described. Literature on flower Flies is diffuse. There are no modern monographic treatments and only a few revisonal revisions. Recent and major works are primarily restricted to systematics. No comprehensive work on biology has ever been published. Francis Gilbert (1986, HoverFlies. Naturalists' Handbooks 5, vi + 66 pp. Cambridge University Press, Cambridge) provide excellent introductions to the flower Flies. There is a list server that cover the group.
Flower Fly Genera
Nearctic Flower Flies
Flower Flies of Costa Rica