Explanation of Names
SCUTTLE FLIES: refers to their habit of running quickly in short bursts, followed by short pauses
COFFIN FLIES: larvae can be a pest in mausoleums, entering coffins and feeding on the bodies inside
Numbers
376 described species in 50 genera in North America (
nearctica.com); half of these species are in one genus,
Megaselia
about 3,800 described species worldwide, and probably ten times that number undescribed
Size
Adult length 1-7 mm; many are in the 2-4 mm range
larvae to 4 mm
Identification
Tiny black, brown, or yellowish flies with a humped back, a low small head, and dark eyes; costal vein extends only about halfway along anterior wing margin; two strong longitudinal veins anteriorly (in costal area), and 4-5 weak veins posteriorly, not connected by cross-veins; hind femora enlarged and flattened, and hind legs long; antennae appear 1-segmented
Habitat
The way of life of most species is unknown. A few common, synanthropic species, especially Megaselia scalaris, Dohrniphora cornuta, Megaselia rufipes, and Puliciphora borinquenensis, live in almost any type of decaying organic material. Larvae of D. cornuta often build up to huge populations when sewer pipes break and nutrient-rich water soaks into the soil; adults emerge in swarms through drain pipes in affected houses. The most commonly noticed species of phorid is M. scalaris, which is found in a number of filth-fly situations, and also infests nearly every type of invertebrate and small vertebrate cultures, such as insect zoos, tarantulas, lizards, snakes, hermit crabs, etc.
Most species, however, are probably specialized scavengers, predators, parasitoids, and even true parasites. Many Megaselia species are found in fungi, some feeding on the fungus (including a few commercially important pests), others probably feeding on sciarid larvae. Many species are found in buried carrion, away from competition from blow flies and other agressive species. One such species, the coffin fly, is found commonly on buried human bodies. Small invertebrate carrion, such as snails, slug, and dead insects, are also breeding sites for phorids. Species of the genus Anevrina are found in the burrows of mammals, probably as scavengers.
Many species are associated with ants, as commensals in ant nests or as parasitoids. The largest group of ant-parasitoids, Apocephalus, are known as ant-decapitating flies because they develop inside the ant's head, and some species cause the ant's head to fall off, sometimes before the rest of the body stops moving. Most North American Apocephalus attack ants in the genera Camponotus and Pheidole, but other hosts are used here and elsewhere. Another ant-parasitoid genus is Pseudacteon, whose South American species are being used in attempts to biologically control imported fire ants (since the native Pseudacteon are not doing the job!).
Other parasitoid genera attack millipedes (phorid genus Myriophora), fireflies and cantharid beetles (some Apocephalus), bees (some other Apocephalus), scale insects, beetles, and probably many other hosts we do not know about.
Some phorids have wingless or short-winged females. Some of these are commensals or parasitoids associated with ants, others are scavengers that are apparently not associated with ants.
-Brian Brown
Food
Larval food is unknown for most species, but phorids are known to be one of the most biologically diverse families of insects. There are scavengers (some extraordinarily generalized, others highly specialized), herbivores, fungus-feeders, predators, parasitoids, and true parasites. Adults feed on honeydew, on nectar in flowers, on dead insects and other carrion, on hemolymph of hosts (in some parasitoids), and a few are known to be predaceous on other insects
Life Cycle
A female of Megaselia scalaris is capable of laying 20 eggs at a time and about 500 in her lifetime. Eggs are laid near suitable host material and larvae hatch in 24 hours. The larvae feed for 8 to 16 days and then crawl to a drier spot to pupate. The life cycle can be completed in 14 days under ideal conditions, but it can take as long as 37 days.
[text by Louisiana State U.]
See Also
"Fruit flies" such as
Drosophila are similar in body size (see comparison photos of
D. melanogaster and
Megaselia scalaris on page 4 of
this PDF doc) but have a larger head and bright red eyes in life and crossveins in their wings.
Internet References
pinned adult images of undetermined
Megaselia species (Insects of Cedar Creek, Minnesota)
close-up images of undetermined adult
Megaselia species (Alan Hadley, micropics.org, UK)
Questions and Answers on phorid flies (Brian Brown, Los Angeles County Museum of Natural History, phorid.net)
overview of habits and biology and common name reference [Scuttle Flies] (Alan Christensen, U. of Nebraska)
aquatic phoridae description, biology, and common name reference [Humpbacked Flies] (Ethan Bright, U. of Michigan)
origin of the name Coffin Flies (Australian Museum, deathonline.net)
general overview of habits, description, biology, and control (Louisiana State U.)
account of myiasis [invasion of living tissue by dipteran larvae] by
Megaselia scalaris in wounds of hospital patient (P.R. Hira et al, Kuwait U., Kuwait, courtesy of US National Institutes of Health)
