Of all insect species, at least 97 percent found in the home and garden landscape are beneficials or innocent bystanders, according to the Maine Cooperative Extension Service
Most beneficial insects in their adult state eat pollen and/or nectar. To attract them, plant flowers such as most annuals that bloom for a long time. Small-flowered plants, including many herbs and weeds (such as chickweed) are paticularly attractive to tiny parasitic wasps.
The list of plants that beneficials love includes parsley, dill, fennel, members of the mint family (lemon balm, spearmint, thyme), daisies, coneflowers, and goldenrod.
Other common nectar-producing plants include asters, bee balm, black-eyed susans and other rudbeckia), borage, buckwheat, clover, cosmos, Joe-Pye weed, lavender, marigolds, members of the onion family, rasberries and other brambles, sage, marjoram, and tansy. And the list goes on.
The trick is to have a highly diversified garden and landscape to attract the beneficials that chomp and chew and digest the bugs that eat your veggies.
I keep seeing live beneficial insects offered in catalogs, but I see no sense in bringing them home and offering them nothing for lunch.