Why Are Big Black Flies in My House? By Hallie Engel SAVE; Few sites are so disconcerting as a swarm of big, black flies buzzing around the house. Not only are flies hard to get rid of, they spread bacteria collected from landing on feces, dead animals, garbage and other unpleasant things. By creating an account you agree to the Hunker May 16, 2016Sunday I go into the basement and again there are probably 10 flies again. Sunday night 12 flies (get rid of them) Monday morning 12 flies (working on getting rid of them). Nothing in the basement smells like rot, death or decay (what google told me to look for). The most common reason for flies swarming all over your house is an infestation inside or nearby your home. If you suddenly see a swarm of flies that means dozens of eggs have already hatched and developed into flies. The source is likely inside your house. I do not want flies hatching in my house! They are gross looking and their story is kinda gross but if you check this out you will not worry that they are coming from some dead mouse in the basement! Cluster flies have a completely different life cycle. These flies are common inside houses. Cluster flies have a completely different life cycle. These flies are common inside houses in fall and winter. The life cycle of the cluster fly begins in the spring when they leave the overwintering sites and lay their eggs in the soil. The larval or maggot stages of this fly attack and eat earthworms. I cannot think out of some possible way for the flies to come in. There was an envelop slip on the front door, but it was by default closed, unless people from the outside want to deliver some mails to the inside. There was also a pipe stretching from the basement to the outside, for letting out vapour of heating during winters. Sep 28, 2017Flies in the basement are likely drain flies, which lay eggs in the muck inside stagnant drain pipes. They are really tough to get rid of. Raid the area, and draino the sludge, rinsing it out repeatedly with boiling water several times over a few days. May 31, 2011Two common causes of a sudden fly infestation are: 1. Not throwing out your garbage often enough. Flies will lay eggs in almost anything that's soft and rotten. The larvae and pupae of the moth fly live in the thin gelatinous film found in drains, septic tank field lines or filter stones. The larvae feed on sediment, decaying vegetation and microscopic plants and animals. The larval stage lasts from 9 to 15 days before pupating. Aug 19, 2009I get swarms of flies every year on really hot days. The flies are looking for a cool spot to hang out and lay their eggs. I always find the larvaes in my kitchen at spots such as the garbage can and underneath my table. Despite screens on my doors and windows and cleaning my kitchen, it only take one fly to give birth to a swarm of flies. Aug 25, 2010It did not have any flies around it, but he threw it out and within a day or two the flies went away. posted by Lucinda at 5: 21 PM on August 25, 2010 We had a rat in our basement once and my landlord set out traps, but we never saw it again or found the body. An infiltration of the basement by insects such as flies often indicates a breach somewhere between the foundation and topsoil where flies find food. These flies will infiltrate a basement through several possible entries and for several reasons. One possible reason for dead flies in a basement is the presence of a larger carcass. Aug 12, 2008Indoor and Outdoor Insect and Pest Control House Flies in Basement Hi, We've got a problem with house flies. Yesterday I think we must have killed at least 100 flies in the basement (finished House Flies in Basement DoItYourself. com Community Forums We had small, black, heartshaped flies in our basement, about 12 the size of house flies. The pestcontrol person said they were drain flies coming from our sump pumpstand pipe combo for water control. Some boiling hot water and dish soap in the sump pump and in the stand pipe cured them.