Do It Yourself Drain Fly Control

Moth Fly
 
Photo Credit: Tom Myers
AT A GLANCE: 
Size: 3/16 - inch 
Color: Brown to gray or gray-black 
Top of Prothorax: Hairy, no markings 
Other Identifying Characters: 
All wing veins run parallel to each other; body and wings covered by numerous short hairs

ID Tips. Moth flies are small flies up to 1/8-inch in length including the wings. They are usually black in color although at least one species found in structures has a brown body and wings. The entire body and wings of the moth fly are covered with tiny hairs giving it a moth-like appearance. 

Basic Biology. The moth fly is commonly called the drain fly because it usually is found breeding in drains which brings it into contact with potentially disease-causing bacteria. This could result in these organisms being carried onto food products or into sterile areas in hospitals. 
     Moth flies develop by complete metamorphosis. The life cycle begins when the female finds a suitable medium in which to lay her eggs. The eggs are laid on the surface of the gelatinous film inside a drain or on top of decaying organic matter. The larvae live inside the gelatinous film of the breeding material and breathe by extending a breathing tube through the film. The larvae feed for up to 15 days before pupating. The entire life cycle can be completed in as little as 8 days or as long as 24 days, depending on the temperature. 

Key Inspection Tips. Finding the breeding sources and eliminating them is the key to eliminating a moth fly infestation in a building. Since moth flies typically breed in drains, this is a good place to start the inspection. Moth fly larvae live in the moist film that develops on the sides of a drain and in the drain's trap. The presence of numerous adult flies inside a drain is a good sign that the drain is a breeding site. Use a knife or screwdriver to scrape the film off the sides of the drain and examine it for live larvae. 
     Occasionally, drain pipes will break under slab floors or between floors in commercial buildings. Moth flies can breed in large numbers in the organic debris deposited through the break in the pipe under the slab. Adult flies then enter the living space above the slab through cracks in the slab and back through the drain pipe. To determine if these flies are exiting through cracks in a floor or from a drain, place pieces of masking tape over the crack or the drain opening. Leave space between the strips of tape to allow air movement for the flies to follow. If flies are exiting the openings, some of the them will become stuck to the tape. If the suspicion is strong enough that moth flies are breeding under a slab, a hole must be broken through the slab to see if indeed a pipe has broken and flies are breeding there. After a hole is broken through the slab, poke around and dig in the soil under the slab. The organic debris and moist soil may actually be several inches under the surface. The presence of fly larvae and/or adults confirms the site as a breeding source. 
     Sump pump pits and sewers are usually found in a basement area and also prime breeding sites for moth flies. Sump pump pits and sewers should be checked for activity even if they are not located close to the area where flies are seen. The flies might not always be breeding close to the infestation area. 
    In homes, moth flies are generally found breeding in bathroom drains, particularly those in showers. Shower pans are prone to leaking and the area under the shower pan becomes a prime moth fly breeding source. If suspicion is strong that flies are breeding beneath a shower, it may be necessary to drill a hole into the area under the shower pan or the wall behind the shower. In most cases where moth flies are breeding in this area, adult flies will begin emerging from the hole within minutes. Moth flies are strongly attracted to light and will fly to the hole drilled through the wall. 
     Moth flies will also breed inside crawlspaces. In many of the cases where this occurs, a drain pipe is leaking into the crawlspace. Inspect the crawlspace if one is present and look for adult flies. Check spider webs for dead moth flies if live ones are not seen in the crawlspace. 
     Don't stop looking when one breeding source has been found. In most cases, several breeding sources will be present.

Phorid Flies
 
Photo Credit: Tom Myers
AT A GLANCE: 
Size: 1/8 - inch 
Color: Light to dark brown 
Top of Prothorax: No markings 
Other Identifying Characters: 
Small head; sharply arched (humped) thorax

ID Tips. Phorid flies are small flies up to 1/8-inch in length including the wings. They are usually tan to dark brown in color. A key character is the severe arch or humpbacked shape of its thorax compared to its small head, thus it is also known as the humpbacked fly. The phorid fly lacks the red eyes of the fruit fly—the fly with which it is most often confused. 

Basic Biology. Phorid flies are found throughout the world and are a serious pest when found in food producing or food handling facilities. This fly breeds primarily in and feeds on moist decaying organic matter. Because it frequents such unsanitary areas, it could potentially carry diseasecausing bacteria onto food products. 
     Phorid flies are a particular concern in hospitals and other health care facilities. Phorid fly larvae have been found in open wounds of patients and in laboratory petri dishes which might result in potential contamination due to bacteria which might be found on their bodies. 
     Phorid flies develop by egg, larvae, pupa, and adult. The tiny eggs are deposited on or near the surface of decaying organic matter. The female will deposit about 20 eggs at one time, and the larvae emerge in 24 hours and feed for a number of days (8-16) depending on food and temperature. They then crawl to a drier spot to pupate. Under ideal conditions, the life cycle from egg to adult can be completed in as little as fourteen days but may take as long as 37 days. 

Key Inspection Tips. Finding the breeding sources and removing them is the key to eliminating a phorid fly infestation in a building. This is many times easier said than done. When searching for the breeding sources of phorid flies, keep in mind that the larvae can survive only in moist, decaying organic matter. The first spot that should be checked are the floor drains, if any are present. Fly larvae live in the moist film that develops on the sides of a drain and in debris which may become trapped on the edge of the drain. The presence of numerous adult flies inside a drain is a good sign that the drain is a breeding site. Use a knife or screwdriver to scrape the film off the sides of the drain and examine it for live larvae. 
    Occasionally, drain pipes will break under slab floors, and phorid flies can breed in immense numbers in the organic debris deposited through the break in the pipe under the slab. To determine if phorid flies are exiting through cracks in a floor or from a drain, place pieces of masking tape over the crack or the drain opening. Leave space between the strips of tape to allow air movement for the flies to follow. If flies are exiting the openings, some of the them will become stuck to the tape. If the suspicion is strong enough that phorid flies are breeding under a slab, a hole must be broken through the slab to see if indeed a pipe has broken and flies are breeding there. Poke around and dig in the soil under the slab. The organic debris and moist soil may actually be several inches under the surface. The presence of fly larvae and/or adults confirms the site as a breeding source. 
     Trash containers which are not cleaned regularly are another good source for phorid flies. Phorid flies will also breed in any moist, decaying organic matter trapped in cracks of kitchen equipment or under the bottom of such equipment where it meets the floor. To determine if flies are breeding below the bottom of equipment, use a knife or small spatula to scrape any debris from inside the crack. If live fly larvae are found in this debris, the crack is serving as a breeding site. 
     Flies are not always breeding near where they are found. Because they fly, the breeding source can be located in another room, on another floor, or even outside. It is common to find phorid flies breeding in or under dumpsters then making their way into the building. Don't ever assume that because fruit flies are seen in particular room that the breeding source was located there. 
     Other sites where phorid flies might be found include garbage disposals, rotting meat and vegetables, the overwatered soil of potted plants, and fresh flowers in vases. They have also been found breeding in dirty mops in janitor closets and laundry rooms, animal feces, faulty septic systems, and human cadavers. They are a common and most unwelcome pest in mortuaries, morgues, and mausoleums. In one case, an infestation was traced to a bucket of animal-based glue used in a book binding factory.
     Don't stop looking when one breeding source has been found. In most cases, several breeding sources will be present.

Courtesy of Pest Control Technology