we have the same problem, and folks at my husband's work said its common in summer. We just moved here, so folks like to give us a big rash about things, i.e. about how cold its going to be etc. so we take everything at face value. But its pretty bad. We have tried several home remedies we read on the internet but to no avail. Being from the Caribbean, where houses are open, we are used to keeping our doors open but we have had to shut ourselves in. We also never leave food out, or dishes in the sink-- something years in the tropics taught us (but there its cockroaches and tree rats you worry about). If you find something let me know- i'm off to buy that weird sticky fly paper today - will definitely do nothing to improve the look of my house to have dead flies hanging from yellow sticky paper everywhere- but its all I can think to do.