Which flies show up in Washington homes
Start with size and behavior rather than color. A quarter-inch dull gray fly on the window that flies well and lands on food is a house fly, and it came from outside. A slightly smaller fly with a hairy body and wings held flat like a tiny tent, sitting on tile and barely moving, is a drain fly, and it came from a pipe a few feet away. The one worth learning is the phorid fly. It is small and tan, it has a noticeably humped back when you see it from the side, and it prefers running across a surface in short darting bursts to flying. That running habit is diagnostic. In western Washington, phorids near a floor vent or a crawlspace hatch usually mean wet soil below. Bigger flies with a metallic blue or green sheen are blow flies. They breed on carcasses, so a group of them appearing indoors is information rather than a nuisance. Fungus gnats, the delicate dark ones that drift out of plant pots, are the most harmless of the set and the easiest to fix.
The Washington fly year
March and April bring the first activity, usually on the sunny side of a house during a break in the rain. Outdoor material is warming but still cool, so populations build slowly and this is the cheapest moment to clean up. June through September is the productive stretch, though productive means something gentler here than in a hot state. At a median summer high of 77 degrees, each generation takes longer, so what you notice is persistence rather than volume. East of the Cascades the arid summer runs hotter and faster, and the sources are concentrated in irrigated ground. October and November tail off as the rain returns in earnest. With a median winter low around 35 degrees, western Washington rarely gets the hard freeze that ends things outright, so a mild December can still produce the occasional outdoor fly. Meanwhile indoor sources carry on at full strength. If your fly count is flat from November to February, you are looking at drains, a crawlspace, or something dead, and the yard has nothing to do with it.
What a real crawlspace inspection covers
If you have a crawlspace and a persistent small fly problem, the inspection that matters happens under the house, not in your kitchen. Someone should open the hatch and go in with a light rather than shining one from the doorway. What they are checking: whether the vapor barrier is intact and overlapped, whether the soil under it is wet, whether any supply or drain line is dripping, whether ducts are sweating, and whether standing water sits anywhere after Washington's wet season. They should also look for evidence of animals, since a dead rodent in a crawlspace produces a blow fly emergence upstairs a couple of weeks later. Ask them to photograph what they find. A phorid job often turns into two jobs, one for the plumber or the crawlspace contractor and a smaller one for the pest side, and photographs make that conversation straightforward. If a provider quotes fly work on a home with a crawlspace without ever entering it, they are guessing, and you will be paying for repeat visits that never reach the source.
What moves the price in Washington homes
Access is the first variable. A tight crawlspace with low clearance takes longer to inspect and treat than an open basement, and some homes need a hatch enlarged before anyone can work. That labor shows up in a quote before any product does. Scope is second. Drain work priced for a single bathroom is a different job from drain work covering a kitchen, two baths, a laundry, and a basement floor drain, and larger homes in Bellevue or Seattle usually mean the second version. Ask exactly which fixtures the number includes. Third is what falls outside pest control entirely. Replacing a vapor barrier, correcting grade so water stops draining toward the foundation, repairing a leaking line, or removing an animal from a wall are separate trades. In wet western Washington those items are frequently the bulk of the real cost, so a low pest quote that excludes them is not the bargain it looks like. Ask each provider to list exclusions in writing alongside the identified source.
How to compare two Washington quotes
Put the bids side by side and ignore the totals for a minute. Four things determine whether a plan works. Did anyone name where the larvae are living? A quote that describes products and visits but never a location is priced to kill adults, and adults are the symptom. Second, does the follow-up schedule fit the biology? Emergence keeps happening for a while after a source is removed, so returns spaced a couple of weeks apart make sense in a cool climate and monthly returns often do not. Third, is the coverage the same on both bids, fixture for fixture and area for area? Fourth, does either one include work under the house, and if so what specifically? Then ask the question that sorts them fastest: what are the maggots eating, and where did you find it? A provider who has been in the crawlspace and looked in every trap will answer immediately. One who has not will change the subject to product names.