Sealing your house against roof rats and scorpions is not full proof and cannot guarantee no entry. But, if you're going to seal your house, you might as well do a scorpion seal instead of a rat seal. In effect, they are the same thing and the cost should be not that different. Thus, the difference is a finer metal mesh for sealing vents and a different compound for caulking spaces.
As to small flies hovering on a window sill, you do not need to waste money and pollute with any kind of poison or strain yourself swatting. Just spray them with water and vacuum them with a nozzle vacuum. Actually, if you have a good strong vacuum, you don't even need to spray them with water. Turning on the vacuum will not scare them and once the nozzle ends gets close to a fly, it cannot escape the vacuum's pull.
It is convenient to keep a cruet of vinegar out along side your cruet of organic extra virgin olive oil. But at this time of the year (in Phoenix), you likely will see that the vinegar attracts jiggers. If so, empty your vinegar cruet, wash it in the dishwasher, and stop using it until jigger season is over.