Northern catalpa draws summer insects

The air around the northern catalpa carries the weight of summer heat and the faint sweetness of its late-season blooms. These threatened trees stand scattered through Indianapolis's neighborhoods, their broad heart-shaped leaves casting wide pools of shade. If you are walking beneath one now, look up through the canopy for clusters of white flowers marked with purple and yellow spots, each bloom shaped like a small trumpet opening to the longest days of the year.

The northern catalpa times its flowering to coincide with peak insect activity. While most trees finished blooming weeks ago, catalpa waits until deep summer when the breeding season reaches its height. Each flower cluster holds dozens of individual blooms, each one producing nectar accessible to insects with varying tongue lengths. The flowers open in sequence over several weeks, extending the feast through July's heat when other nectar sources have dried up or gone to seed.

This timing draws the Eastern Eyed Click Beetle and dozens of other insects to the catalpa's crown. The click beetle, with its distinctive white eyespots on a black thorax, visits the flowers for nectar but also hunts smaller insects attracted to the same blooms. Catalpa flowers pull in everything from tiny sweat bees to large carpenter bees, from hover flies to butterflies. The tree becomes a temporary feeding station where predators and pollinators share the same branches. Beetles browse the flower clusters while bees work individual blooms just inches away. The catalpa's extended flowering period supports multiple generations of insects through the peak breeding season, when females need extra energy for egg production and males compete for territory.

The relationship extends beyond the flowers. Catalpa leaves feed the larvae of the catalpa sphinx moth, which appears nowhere else in the ecosystem. Adult sphinx moths emerge in waves throughout summer, their thick bodies and rapid wingbeats making them important pollinators for evening-blooming plants. The tree's broad leaves also shelter jumping spiders like the Dimorphic Jumping Spider, which hunts the smaller insects that gather on the leaf surfaces. When catalpa pods form in late summer, they provide winter shelter for overwintering insects, extending the tree's support through the cold months.

The white trumpet flowers catch the afternoon light filtering through the broad leaves above. Each bloom opens for just a few days before dropping its petals, but new ones continue opening in the cluster. Listen for the steady hum of wings around the flowers, the sound of summer's breeding season sustained by this threatened tree's perfectly timed abundance.