These critters have good spatial memories that keep them coming back, night after night

It’s always a treat to spot Zebra Longwing butterflies (Heliconius charithonia).

These exotic-looking insects are common in Mexico and Central America, and they’re found year-round in parts of Texas and most of Florida, where the species is the state butterfly.

In South Carolina and a few other states, Zebra Longwings are considered occasional to common visitors during late summer and fall. Look for them along the edges of woods and in open areas, such as gardens and parks.

As butterflies go, they are medium-sized, with elongated black wings marked by pale yellow stripes. They’re attracted to lantana, verbena, and other nectar-rich flowers, whose nectar they sip via straw-like mouthparts.

Zebra Longwings also feast on pollen, a high-protein food that enhances female egg production and extends adult lifespan a few months beyond the usual period (several weeks) typical of most butterflies.

Toward the end of the day and during cool or rainy weather, the butterflies pack together in communal roosts that may contain dozens of individuals. Aggregating helps keep them warm, and it may give some protection against predators.

Studies have shown that Zebra Longwings have well developed spatial memories and return to the same roost sites night after night.

The caterpillars spend most of their time eating the leaves of passionflower vines, including maypop (Passiflora incarnata), a common species in the Southeast. While feeding, larvae sequester plant toxins that make them unpalatable to many predators. Their conspicuous color pattern (white with black spots) is thought to act as “warning coloration,” advertising their unpalatability. This toxicity persists into adulthood.

Perhaps the most striking feature of Zebra Longwings, though, is how they pair up and mate.

Soon after completing the pupal, or chrysalis, stage and morphing into adults, male butterflies start searching for females that haven’t yet completed metamorphosis.

Once a male locates a female chrysalis, he perches on top of it and vigorously fights off other males. He may return to the same chrysalis day after day, even for a week or so, defending his future mate.

There’s more. The male may initiate mating as the adult female starts to emerge, but he may also pierce the chrysalis ahead of time and transfer sperm before she even comes out.

“Pupal mating,” as this extraordinary behavior is called, has been recorded in only a few other butterflies besides Zebra Longwings.

How do searching males distinguish female pupae from male ones? It turns out that their odors are different. Males release a substance called linalool, and females emit linalool oxide. Using their antennae, male butterflies can smell the difference.

Interestingly, they sometimes make mistakes. But studies have shown that males get it right about two-thirds of the time.