One morning early in April of 1998, when I was visiting people in Florida, I saw long, thin streams of cabbage white butterflies here and there going north. They, apparently, were migrating to alfalfa hay fields farther north to sip nectar from flowers and lay eggs on the plants.
One warm, sunny afternoon in October of 2014, I saw many autumn meadowhawk dragonflies cruising back and forth low over the six-acre swimming lake at Mt. Gretna, Pennsylvania. Apparently they were migrating south, but stopped at that human-made impoundment to catch and eat flying insects over the water. In the bright, low-slanting sunlight, those striking dragonflies had abdomens as red as the autumn foliage on the red maple and black gum trees that bordered the lake.
And during a couple of days early in May of 2012, thousands of red admiral butterflies fluttered north low to the ground almost everywhere in Lancaster County, Pennsylvania. They flew low over lawns where I worked, across rural roads on the way home and over our lawn at home, for example. They were a spectacle I haven't seen before nor since. Those red admirals were migrating north to mate and lay eggs on the three-feet tall and still growing stinging nettle plants.
Pretty, medium-sized butterflies, red admirals have brown and orange upper wings. Females of this species lay eggs on stinging nettles, one of the few plants their caterpillars eat. Those larvae hatch during the second week in May and pupate by mid June, stripping many leaves off their stalks in those few weeks. By early July, this second generation emerges as beautiful adult butterflies and feeds on the nectar of purple cone flowers and other species of flowering vegetation. Some of their offspring will migrate south to avoid the northern winter.
Some people don't know it, but several kinds of insects, including various species of butterflies, moths, dragonflies, beetles and others migrate according to the seasons, including some species here in southeastern Pennsylvania. They are another intriguing part of the miracle of nature.
The famous monarch butterflies are the best-known of insect migrants to Americans. There are four generations of monarchs every year. Early in March, the first of any given year starts journeying north from wintering grounds in the middle of Mexico, southern California and southern Florida. That generation migrates a few hundred miles, mates, lays eggs and dies. The second generation continues the passage north, mates, lays eggs and dies. The third generation does the same, but the fourth pupates late in August and emerges early in September, with each individual ready to migrate south to one of three major wintering grounds. And what is so miraculous about the fourth generations' southbound migrations is that no monarch of that generation had ever been to the wintering grounds, yet they all unerringly find their way to one of them! That is one of many miracles of nature. How do they do it?
I have seen alfalfa and red clover hay fields bursting with blossoms and loaded with butterflies seeking nectar, including several monarchs in each field. Some fields seem to shimmer with fluttering butterflies. It's always inspiring, and a treat, to see those multitudes of butterflies, including the striking monarchs, sipping nectar from the flowers and moving to other ones to feed.
I have seen spectacular, spell-binding, south-bound migrations of monarchs in September during a few autumns through the years. Sometimes they go by any given point of land at the rate of one every few minutes or less, all heading south or southwest. Sometimes they go by in seemingly little flocks. And a couple of times, several monarchs have spent the night in one or two of our trees on our lawn, but are gone the next morning; continuing on their way.
The caterpillars of monarchs consume only the leaves of several kinds of milkweeds. Female monarchs must lay their eggs on milkweed foliage for their young to survive and pupate.
Common buckeyes are a striking species of migrating butterflies. They are mostly brown on top, with two large, "fake" eyes on the top side of each of four wings. Those eyes must be startling to a bird of other creature that intended to snare a buckeye to consume. Buckeyes' larvae ingest a variety of low herbs in fields and along country roadsides.
Green darners are a kind of large dragonfly that have green thoraxes, pale-blue abdomens and four clear, stiff wings, with a six-inch wingspan. Adults feed on flying insects over ponds and fields, and while on migration to The South for the winter. Their larvae, or naiids, like those of all dragonflies, feed on aquatic insects, tadpoles, small fish and other small critters on the bottoms of their nursery ponds. Those larvae have gills to "breathe" while underwater.
When mature, naiids climb up plants, emerge from the water and shed their larval exoskeletons. When their wings are ready, these adult dragonflies take flight to search for food and mates.
Swarms of southbound green darners can be spotted almost anywhere during late summer and into fall, looking for all the world like tiny helicopters. Sometimes they will be cruising about and catching insects to eat on the wing, creating spectacular and entertaining aerial shows.
Twelve-spotted skimmers are another striking kind of dragonflies, so-named for the black spots and white spots on each of four wings. This species engages in sporadic, irruptive migrations at times. And this species, and its relatives the handsome white-tailed skimmers, are common around ponds in southeastern Pennsylvania during summer.
These are just a few, example, insect migrants. Some readers may encounter one or more of these species, or others, migrating north or south, depending on the season. Some encounters will be spectacular and inspiring.
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