Its pronounced lemon scent recalls citronella (but in a far more appetizing way). In fact, the plant has high levels of citronella, a compound bugs strongly dislike.
We may enjoy the heavenly scent of lavender, but critters politely disagree. The best variety is lavandin, which has a high concentration of camphor, which keeps bugs far away.
Though it sounds like something your favorite Italian grandmother would recommend, a pot of basil really can help you enjoy the outdoors in peace. It's one of the few plants that emit a strong scent without having to crush the leaves.
Pro: Mosquitoes hate catnip. Con: You will quickly meet your future new pet within moments of putting the plant out.