If this is not feasible, ask the host to advise the guests not to wear perfume, which attracts insects. Perfumes are flower based and attract all kinds of winged insects, including bees and wasps. Bright colors also attract bees. Likewise, while it may be nice to hold the event in the middle of a flower garden, remember that bugs and bees find flowers attractive also. Plan your party so that guests can see and enjoy the flowers without being close enough to upset stinging creatures.
Mosquitos love warm, moist, moving bodies.
Guests that are warm, perspiring and wearing perfume are the best targets. The insecticide pyrethroid is deadly to mosquitoes. Or you can suggest that the guests incorporate sprigs of the citrosa plant into centerpieces and floral arrangements. The citrosa plant emits an odor of citronelia that repels mosquitoes. Bees and yellowjackets are attracted to food and will sting the hand that shoos them away.