Bees develop an innate sense of where the picnic food is, especially on warm summer days.
In fact, experts say yellow jackets can actually learn where to find good food, and even when it will be placed on the table. They tend not to hang around much in the morning, but will fly in just before lunch is served. To discourage these uninvited visitors, cover food and drinks when dining outdoors. Be alert to other stinging insects too. Wasps, for example, are attracted to sweet drinks and will even climb inside pop cans.