The true origin is unknown, as these flies are found throughout the world.
This is one of the largest filth flies to be found in and around structures, and its presence indicates that larval food resources such as animal feces or a dead animal are present. The adult flies often overwinter, commonly within structures, and they may appear within the structure during warm winter days. They are drawn to light, such as windows and doorways. The maggots are commonly found in fresh wounds in humans or animals and are even used in medical maggot therapy. The life cycle from egg to adult fly ranges from 10 to 25 days, depending on temperature, and the maggots pupate in the soil or beneath the carcass they have been feeding on. When feeding on a carcass within a structure the maggots often wander away from that carcass when mature, seeking a protected crevice in which to pupate. This often results in maggots falling from openings in the ceiling when the food source is in the attic above.
While it is called the “blue” blow fly the adult flies are actually a dull metallic blue on the abdomen and nearly a dull black on the thorax. They are very large, often over ½ inch in length, and fly with a very loud “buzzing” sound. The top of the thorax has several indistinct darker stripes running front to back. The larvae are typical “maggot-shaped” with a strongly narrowed head and widened posterior. The spiracles at the posterior end are very similar to the maggots of Green blow flies with 3 elongate-oval rings (the respiratory slits) set within another ring.
Characteristicts Important to Control:
The presence of blow flies in and around structures indicates there are food resources for the larvae, as the adults are strongly attracted to the odors of rotting organic materials. Meat is a favored food of the larvae and dead animals within structures will breed large numbers. Finding the food resources and eliminating them is necessary for complete control of the problem.