Why one flat in a Chicago three-flat gets flies and the others do not
In stacked Illinois housing, the unit with the flies is often not the unit with the source. Three-flats and courtyard buildings share a back stair, an alley, a basement, and usually a drain line, and a fly that hatches in a wet corner of any of those goes toward the nearest lit kitchen after dark. Start by mapping instead of scrubbing. Put a cup of cider vinegar at your sink, another on the back porch or landing, and a third near the basement door, and compare the catch each morning for three days. The heaviest cup points at the source. If it is the porch cup, the alley cans or a neighbor's recycling are producing, and no amount of counter wiping will fix it. If the source is inside your kitchen, clear it. If it is shared, take the count to the owner or the association with a request to hose and dry the cans, rinse the recycling area, and check the basement floor drain.
The Illinois fruit fly year, month by month
January through March is the quiet stretch. Outdoor stages are gone at a 17F median winter low, and any flies you see are breeding in a disposal, a recycling bin, or a forgotten bag of potatoes. April through June builds slowly. Grocery produce ripens faster on the counter as kitchens warm, windows start opening, and a first small hatch usually shows up around Memorial Day. July through October is the real season across Illinois. Tomatoes, sweet corn, melons, peaches, and cider come in by the box, kitchens hold near 84F, and 70% humidity keeps bins and mops damp. The eight to ten day cycle the University of Maryland describes runs at the short end, and a few hitchhikers on a farmers market bag become a crowd in a week. November and December taper outdoors while indoor cooking picks up, so holiday kitchens in Naperville or Springfield often see one last flare before the cold finishes it.
Bars, taprooms, and the drain nobody scrubs
In a bar, the fruit flies are usually not coming from the fruit. Beer runs into the mat and under the cooler, the soda gun holster collects syrup, the dish pit stays wet through service, and the floor drain grows a film that never dries. The common mistake is pouring bleach or boiling water down the drain. What works is mechanical: a long brush to break the film loose, then a bacterial foam that keeps consuming residue between visits, repeated monthly through the warm season. Ask a provider two specific things before signing anything. First, whether the quote covers the floor drains, the bar mats, the soda gun holsters, and the mop sink rather than just a spray in the dining room. Second, whether they will identify the species in writing, since a taproom with drain flies on a three to four week cycle needs a different schedule than one with vinegar flies rebuilding every eight days.
What a first visit should cover in an Illinois home
A useful first visit is mostly looking, not spraying. In an Illinois house, expect the provider to spend time under the sink, behind the fridge, in the cabinet where potatoes and onions live, at the recycling bin, and at any basement or laundry floor drain, the sites that keep producing after the counters are clean. They should also check the things people forget. The drip pan under a dehumidifier running in a Peoria or Decatur basement, a second fridge in the garage with something leaking in the bottom drawer, a mop left standing in a bucket, and the gasket seam on a garbage disposal all hold enough fermenting residue to feed a generation. In a state where 70% humidity keeps those spots damp well into October, none of them dry out on their own between visits. Ask for three things in writing before they leave: what species they found, exactly where the breeding site was, and whether a return visit inside the next two weeks is part of the price.
How to compare two fruit fly quotes
Two quotes for the same Illinois kitchen can differ by a lot, and the gap is usually scope rather than skill. Check the inspection first. One quote may cover only the kitchen while the other includes the basement drain, the garage fridge, and the trash area, which is the difference between a treatment and a search. In a two-flat or a building with a shared alley, ask specifically whether the common areas are in scope, because the source frequently sits there. Then check the follow-up. A quote that includes a return visit within two weeks is worth more than a cheaper one that does not, since anything in the pupal stage on visit day will emerge afterward. Last, check what happens if the species is wrong. If the provider opens the drain and finds fuzzy moth flies or hump backed phorids instead, does the quote change, and does a suspected leak become a plumbing referral rather than more spraying? Get the answer before the first visit, not after it.