I like to be sure that there are plenty of insects in my garden - at least the good ones such as pollinators and predators. One plant that is a magnet for bees and other beneficial insects is African Blue Basil. It starts blooming in the spring and just keeps going until cold weather whacks it back. If it's left untrimmed through the winter it usually comes back in the spring and can last a few years. It is a beautiful plant that always has a place in my garden. I usually take a few cuttings in the fall,root them in water, pot them up and keep them in a protected place just in case there's a freeze that's hard enough to kill the mother plant.
African Blue Basil
Other ornamental plants that have reliably enticed good bugs to my garden are Sweet Alyssum, Cosmos, Sunflower, Penstemon, and various Verbascums. Many herbs and veggies have also proven to be extremely attractive when in bloom, one of the most attractive in my experience being cilantro.
Bumble Bee on PenstemonOne interesting insect that has visited my garden a few times recently is the Tarantula Hawk. It's a very distinctive jet-black wasp with bright orange-red wings. This critter would be handy to have around if you have a Tarantula problem. The female Tarantula Hawk deposits an egg on the live spider- I won't go into the gory details here, but the spider eventually gives it all for the developing Tarantula Hawk.
I'm working on getting plants into the garden that are attractive to beneficials, off the top of my head what I have so far includes Alyssum, African Blue Basil, Variegated African Blue Basil, Thyme, Yarrow, Penstemon, Chrysanthemum, Rosemary, Eriogonum, Cosmos, Nasturtium