July to the end of October is the time of insects in southeastern Pennsylvania because those invertebrates are cold-blooded and active only during warmer weather.

Some of the more interesting, and obvious, insects in this area include fireflies, true katydids, snowy tree crickets, monarch butterflies, pearl crescent butterflies, differential grasshoppers, wooly bear caterpillars, ladybug beetles, and ash-leafed maple, or box elder, bugs.

These insects are either courting for reproduction or preparing for winter, depending on the life cycle of each species.

Male fireflies flash their cold abdominal lights as they emerge from vegetation most every July evening. Those fireflies continue lighting their beacons every few seconds as darkness descends across the countryside.

And, in the dark of night, their thousands of lanterns sparkle beautifully among trees and grass as males and females congregate to breed. 

Male true katydids begin scraping their wings together continuously each evening in August and September to make a courting sound that resembles “katy-did, katy-didn’t.”

These treetop grasshopper relatives look like green leaves, which camouflages them, and are seldom seen. But their uproarious fiddling in woods and older suburbs, to bring the genders together for mating, is unmistakable.     

Male snowy tree crickets live in shrubbery and chirp steadily every night during August and September to invite females of their kind for mating.

These pale-green, 1-inch crickets are also called temperature crickets. By counting their wing-produced chirps in 15 seconds and adding 40, one can estimate the outdoor temperature. 

The handsome monarch butterflies are famous for migrating to Mexican forests each fall to avoid northern winters. But it’s only the fourth generation of monarchs each year that makes the trip south during September and October.

Each spring, monarchs that spent winter in Mexico push north, sip flower nectar, lay eggs on milkweed plants, and then die. The next two generations each summer consume milkweeds as caterpillars, pupate, and continue north, sipping nectar, laying eggs on milkweed, and dying.

But each year’s fourth generation journeys to Mexico to escape winter.

During October, many hundreds of fluttering, orange-and-brown pearl crescent butterflies, which have 1-inch wingspans, swarm upon thousands of lovely aster flowers in sunny fields, meadows, and roadsides to sip nectar. Asters are one of the last big sources of nectar at the end of each growing season.

Also during October, as a response to colder nights, many differential grasshoppers and wooly bear caterpillars cross country roads.

The large, gray-green grasshoppers leap across those rural roads to find favorable places in soil to spawn eggs before they die in frost. Wooly bears undulate over the blacktop to find sheltered places in the ground to spend the coming winter.

By late October, swarms of attractive ladybug beetles and ash-leafed maple bugs, or box elder bugs, congregate in groups of their own in sheltered places, including under logs, leaf litter, or rock piles, where they will spend the winter in relative safety.

These great gatherings are seldom seen by most people, but it’s still interesting to acknowledge their presence.

These are just a few intriguing insects living in southeastern Pennsylvania. There are many other kinds that offer interest to times spent outdoors.

 

Clyde McMillan-Gamber is a retired Lancaster County Parks naturalist.

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