Help! Flies have invaded my pantry.

Let me start by saying that we never have insects or bugs in the house... yesterday though, we had 6 flies in the pantry buzzing at the window. I proceeded to smash them all dead.

Today we get home from work and there have to be close to 30-40! What is going on?

Do I have to get rid of EVERYTHING in my pantry?

It's combined with my laundry room, so it's HUGE, and I have a big stockpile going... I hate the thought of getting rid of everything. I even store the pets food in there. The dogs food comes from the vet, it's $40 a bag! What do I do?

Flies or moths??

If they are flies, they are more than likely coming in from a window or crack some where. It's happened to me before. I'd come home and there were tons of them at the kitchen windows, and it freaked me out. A few of my windows, when I had them up so the screens let in air, would slide down at the top and let in flies. Another time they came up from the basement (unfinished and just creepy) and would hover around the kitchen windows.

If they are small moths, then they come from boxes foods. And those are an entirely different story to get rid of.

They are the common black house-fly.

I don't know how they got in; we don't keep our windows open... and in fact that window in the pantry doesn't have the option to open. But, we did have a bee in there last summer so there IS a way to get in!

How do I find the crack?

Is it likely that it's my dryer vent since that is my laundry room too?
It's right off the kitchen, pantry on one side, and room for the washer/dryer on the other.

The easy way to find a crack that lets air - and flies - in is to light a candle, and very slowly move it around the perimeter of the room, watching for a flicker. When it flickers, you've found the draft, and can then narrow down the source of the crack!

Hubby just says, "I put something moldy in the trash yesterday." I wonder if that is it. I made him take the trash out AGAIN... ugh.

Crossing my fingers! (And NOT asking what he threw away that was moldy!)