Why were there so many dragonflies along the Chicago lakefront this weekend?

• CHICAGO — “It’s like an invasion!” a woman giggled as she lowered her head and launched her bike through a swarm of dragonflies on the lakefront trail. These large-eyed insects with nearly 4-inch wingspans flew among the crowds gathered along North Avenue Beach and Belmont Harbor to watch the annual Air and Water Show. “They’re putting on their own air show,” an onlooker said. While it ...