Windows and bugs....

Built a new home and the windows installed are the type that have the push buttons to pop them out. They have the drains in the bottom of the sills themselves so water doesn't collect. Problem is it seems as if we get a large amount of flys and lady buggs inside the screen, thus allowing them to come in the house. Is there anyway to stop that by putting some kind of material to plug the holes that wont wash out with the rain?
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