Fuzzy Ball-Moss and the Longwing Slumber Party

Zebra Longwing = Heliconius charithonia

Ball-Moss = Tillandsia recurvata

Spanish-Moss = Tillandsia usneoides

Florida-Privet =  Forestiera segregata

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All Florida nature lovers love the Zebra Longwing Butterfly,  and a romp through Google brings forth its ighlightsh, such as being the Florida state butterfly, and the only local butterfly known to consume pollen.  Its larval hosts are passionflowers.  

Those with butterfly gardens or good luck notice that Zebra Longwings can be social, including communal roosting at night, something biologists have pondered for a long time.  Alfred Russell Wallace, the “other” discoverer of evolution, wrote about it back in the 1870s.  Around my yard and garden the Longwing Committee has been roosting in clusters upside down like a flock of tiny bats each night  on different branches of the same Florida-Privet tree.  You can count on finding them at twilight, about a dozen per bunkhouse.   And that prompts a question…why roost like sardines in a can? There are multiple non-mutually-exclusive explanations for butterfly sleeping gangs: 1.  Protection from cold.  2. A mutual-warning system—when one is disturbed, its wing movements start a chain reaction vibrating everyone awake.   3. Collective display of warning coloration.

Longwings very early in the morning, on Ball-Moss, this on Florida-Privet.

With respect to possibility number 2, alarm system, the other morning I walked up to the huddled sleepyheads, and as I got (too) close they popped off the roost all at once. Ooga ooga!  Somebody punched the fire alarm.   

On possibility number 3,  antipredator warning coloration,  the butterflies are poisonous, and their zebra stripes are interpretably “you’ll be sorry” warning coloration, although other possibilities are conceivable.   With the help of chemicals from passionvine hostplants, the butterflies form cyanide-based heart poisons.  A scrum of them hanging together is a billboard warning. Other observers, by contrast, may think the sleeping butterfly cluster looks like twigs and shadows during their dark-hour roosting time, except for some small bright red marks on the wings.  Either way, entomologist Chris Salcedo (see dig deeper below) found Heliconius butterflies to suffer little predation while roosting.  He interpreted those red markings as signals to late recruits arriving to join the party.   They’re twilight lanterns to guide newcomers to a safe landing. 

Red spots at bases of wings

The roosting group begins gathering loosely before dark.   I’ve been sitting here on a computer this afternoon looking out the window watching the butterflies.   Here is my log of Longwing activity:

3:30 pm bright and sunny: Longwings all over the yard and garden area visiting varied flowers having no special interest in the Privet roosting tree off to the side about 50 feet from a garden full of of flowers.

4:30 pm bright and sunny:  A few butterflies visiting flowers far away from the Privet, and around the Privet an unsettled group of Longwings basking, fluttering, and flirting. 

5:30 pm long shadows: The entire backyard Longwing population hovering closely around and on the Privet, dancing among the branches.  Two earlybirds have roosted together in the nocturnal “bat position.” They are clinging to a large gall on the Privet branch.

6 pm getting dark: The original pair expanded now to a trio, and new group of about 12 clustered, with recruits arriving.

Happy hour arrivals at the roosting tree. This pair later expanded to three’s a crowd. Why are they clinging to a gall on the Privet branch?

Why roost on the Privet?  One reason according to C. Salcedo, the butterflies avoid camping under green foliage which is too humid, the sleepers preferring dryness.  The Privet is deciduous, dry leafless sticks.  Secondly, the Longwings feed on Privet flowers.   A relationship between feeding sites and roosting sites is known for Heliconius Butterflies in general.   During the later afternoon gathering phase, there’s a lot of Privet-flower-feeding goin’ on, as the butterflies have shifted away from the main garden.

You can see the feeding and other good things in this mini-movie. FLUTTER HERE

Last night the slumber party was on a Ball-Moss (Tillandsia recurvata) hanging in the Privet.  They do not occupy Ball-Moss every night, yet I wondered if they like something about it.   There’s no easily located mention on the Internet, but if you Google Image “Zebra Longwing roosting”, you find lots of photos of the butterflies on Spanish-Moss, which is similar to and related to Ball-Moss.   Those fuzzy plants look like they’d be great to grab like one of those shag-covered steering wheels.  Maybe tonight’s gall is a good perch-handle too.   The trio choosing it seems non-coincidental.

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To dig deeper:

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