Local Swallowtail Butterflies Are Missing Their Tails

The Virgin Islands swallowtail butterfly Battus polydamas thyamus has no ‘tails’ on its wings.

Battus polydamas butterflies are fairly common in the Caribbean. However, they have an uncommon status because they are included in the large ‘swallowtail’ family even though they don’t have the characteristic ‘tails’. 

In fact, when I first saw one of these butterflies on St. John, its back wings had been bitten off, so I didn’t realize that it was missing the tail-like extensions characteristic of other types of swallowtail butterflies.

Sometimes predators bite off the bottom of a butterfly‘s back wing.

 In the northeast United States, I have seen other swallowtail butterflies that have their namesake projections clearly sticking out from the bottom edges of their back wings. 

This US Eastern Tiger Swallowtail shows off its distinctive tail extensions.

The swallowtail name refers to birds like Barn Swallows that have long, thin, outside tail feathers, sometimes called ‘streamers’. These thin feathers can improve their ability to maneuver quickly in flight, especially when they chase flying insects. Interestingly, female Barn Swallows seem to be attracted to the males with longer tail feathers — even when the tails get so long that they are no longer helpful for hunting maneuvers and instead create extra aerodynamic drag on the birds’ wings.  

Barn Swallows have forked tails with long outer feathers on the edges.

Swallowtail butterflies probably deal with the same issues of lift and drag as barn swallows, and having tails may actually help them glide smoothly over flowers. But the butterflies’ swallowtails are all pretty much the same size, so probably aren’t a factor for sexual selection. They might be helpful in distracting and scaring off predators, though. When threatened, butterflies sometimes will quickly flick their wings open and closed, showing surprising flashes of bright colors.  

Battus polydamas thyamus butterflies have red-orange spots on the undersides of their wings.

And when birds come up behind swallowtail butterflies and grab onto their back wings, it might be helpful to have a skinny tail part that tears off, to help the butterfly escape and survive — like when lizards lose their tails to predators but escape with their lives. 

However, the tailless Battus polydamas butterfly I saw with the bitten wing seemed to have managed to survive okay too. 

A Battus polydamas thyamus butterfly has white markings along the tops of its wings.

Meanwhile I can’t help wondering why a no-tail butterfly is classified as one of the swallowtails. 

The scientific names we use originally came from a classification system designed by a Swedish naturalist named Carl Linnaeus in 1735. The groupings were based on similarities and relationships he observed in nature. Of course, since then classifications of life forms have become more complex and fluid. New species have been discovered, and more is known about interconnections in evolutionary history, including through DNA sequencing. 

The VI no-tail butterfly is identified as: 

Class: Insecta; 

Order: Lepidoptera (which covers both moths and butterflies); 

Family: Papilionidae (butterflies); 

Subfamily: Papilioninae (swallowtail butterflies); 

Genus: Battus (swallowtail butterflies in the Americas associated with Aristolochia plants); 

Species: Battus polydamas (tailless Battus butterflies); 

Subspecies: Battus polydamas thyamus (tailless Battus butterflies living in Puerto Rico and the Virgin Islands). 

A species represents a set of individuals that can mate with each other and reproduce. Usually a scientific name provides first the genus and then the species. A third name indicates a subspecies with some physical variations, often related to geographical differences, such as living on different islands. Many members of the various subspecies listed under Battus polydamas are located on different Caribbean islands, and they are all tailless. The subspecies found in Puerto Rico and the Virgin Islands is named ‘thyamus’. 

I learned that an important link between the tailed and tailless members of the Battus swallowtail butterfly genus is co-evolution with their host plants in the Aristolochia family. These plants are woody, climbing vines often called pipevine or Dutchman’s pipe because of the shape of their flowers. They sometimes have been cultivated for medicinal purposes, but also can be toxic. The Battus butterflies lay their eggs on these vines and the caterpillars ingest the toxic chemicals, making themselves and the adult butterflies poisonous to predators. 

Another (weird) attribute they share is that their caterpillars have bright orange organs called osmeteria that they can pump up and extend out of their heads like forked tongues, while also emitting a foul smell — as a way to ward off potential predators. Sounds like something we all could use.

So due to their common evolutionary history, different types of swallowtail butterflies share some behaviors and physical attributes unrelated to the tail or no-tail distinction. 

I think that’s a good reason to come up with a more inclusive name for the group. Maybe something like ‘stinky, orange, fake forked-tongue caterpillar heads’ would be more appropriate. 

Native Species Complain About Beach Intruders

 

Native Pearly-eyed Thrashers aggressively monitor the beaches

Over the years people living in the Virgin Islands have brought in donkeys, mongooses, deer, cats and chickens, many of which can now be seen scavenging on the local beaches. The Pearly-eyed Thrashers, locally called ‘thrushies’, consider themselves to have first dibs on food at the beach, and do not appreciate the interlopers.

While it is certainly interesting to see an exotic mongoose at the beach, you might be less amused if one drops in on your picnic and makes off with unattended snacks. 

Mongooses lurk in the bushes and sneak onto beaches to look for food 

I once noticed a paper bag lying on the beach that was shaking strangely. As I went to investigate, a mongoose slid out with a sandwich and snuck off before the owner returned.  

Mongooses were introduced on plantations in the late 1800s, to help catch the rats that had tagged along on boats from Europe and eagerly took to eating sugar cane. The mongooses did deal with some of the rats, but also found other native food sources. Their descendants now not only steal sandwiches, but also raid the nests of sea turtles, ducks, shorebirds and iguanas, and have eaten many of the indigenous lizards and snakes. They also impact trees and plants, consuming seeds, birds that are seed dispersers, and insects that serve as native plant pollinators. 

Meanwhile, rats are still around too, similarly eating eggs, lizards and insects, plus seeds and  plants. 

In addition, cats were brought to the islands, some as pets, and others maybe to help catch the rats. Over the years, many cats were abandoned, or otherwise ended up fending for themselves in the wild. Though there are programs now to feed them and keep them from reproducing, some cats still haunt the beaches and bushes, hunting native lizards, birds and rodents. 

Feral and outdoor cats are avid hunters of island wildlife.

 

You can also see packs of donkeys tromping around, including along the beaches. The donkeys were originally brought to the islands to help with the work on plantations. Later they were used for transportation. Then when cars became available, some of the donkeys were let loose to mostly fend for themselves. 

Donkeys roam in packs along some of the beaches.  

The donkeys normally eat grasses, but will sometimes also chomp or trample on native plants that might be important for island ecosystems. They are also experts at taking food from people’s bags left on the beach, and can become aggressive if you try to shoo them off. They can easily get into backpacks and will cheerfully tear into bags of chips, even though inappropriate food is harmful to them, causing diseases and weird fatty deposits. 

White-tailed Deer are the worst about destroying valuable native plants. They especially enjoy mangrove seedlings, which can damage the capacity of mangrove wetlands to rebound after hurricanes. The deer were transported to the islands many years ago to be hunted for sport, and meat. But hunting them is now illegal, despite their rapid rate of reproduction. They too run freely along the beaches, and you can often see a line in the vegetation indicating how high they can reach when they are browsing. 

White-tailed Deer frolic on the shoreline.

In some areas, introduced birds like peacocks can be seen foraging along the water’s edge, competing with local birds for seeds and berries, as well as insects and lizards. 

Peacocks are omnivorous and voracious eaters.

 

Formerly domesticated chickens, too, compete with wild birds for fruits and other food on the beaches.  

A rooster considers whether or not to eat an overripe starvation fruit (Noni).

The much smaller Pearly-eyed Thrashers are not happy to have their territory invaded.

Although the ‘thrushies’ are resourceful and resilient, they can’t keep all the intruders off the beaches by themselves. And the cumulative impact of so many hungry scavengers has decimated some of the native plants, birds and animals. Others survive only on the smaller cays, where they can sometimes find better protection and seclusion, especially if there are effective rat and mongoose eradication programs in effect.  

St. John Hummingbirds Are Getting Ready for Carnival

Male Antillean Crested Hummingbird hovering 

As colorful dance troupes prepare their costumes and routines for the parade, local hummingbirds are engaging in their own display of fine feathers and cool Caribbean moves. 

 

There are two main types of hummingbirds on St. John: Green-throated Caribs and the slightly smaller Antillean Crested Hummingbirds. The different hummingbird troupes will be competing for attention this summer as they parade their plumage. 

 

The male Antillean Crested Hummingbirds have distinctive bright green headdresses. They can make their iridescent head feathers stand up and flash brightly like a neon sign when they turn their heads to catch the sunlight. This is an impressive move for attracting females, and also blindingly disorienting for would-be rivals, or attackers. 

 

Male Antillean Crested Hummingbird showing green flash of head feathers 

 

The males have additional green feathers on their backs, but mostly plain dark feathers in front. 

The female Antillean Crested Hummingbirds have iridescent green feathers on their heads and backs, with light fronts and low crests.      

 

Female Antillean Crested Hummingbird on nest

 

Meanwhile, the festive outfits for the Green-throated Caribs look pretty much alike for males and females: iridescent green head and back feathers, with shiny blue patches on their chests. They are larger than the Antillean Crested hummingbirds, with longer bills that are also slightly curved. 

 

Green-throated Carib hummingbird 

 

These hummingbirds will not be marching in the parade though. They are experts at hovering in the air, where they can show off their impressive wing speeds of 50 to 80 beats per second. They can also fly backwards and upside down. 

 

Green-throated Carib hummingbird hovering

 

Outside of festival activities, you will often see tiny hummingbirds hovering peacefully over bright blossoms, drinking flower nectar. In return, the hummingbirds provide flowers with much-appreciated pollination services. It all looks so sweet. 

Male Antillean Crested Hummingbird drinking nectar

 

However, hummingbirds are also often fiercely competitive.

 

The males are very aggressive in defending access to what they consider ‘their’ flower patches. They need to eat lots of nectar to power those fast wing beats, so they feed frequently from available flowers. They are quick to dive bomb intruders - not just other hummingbirds but also larger birds like bananaquits - poking at them with sharp bills and tiny talons. And then during breeding season, they will also fight with other males over territory.  

 

Male Antillean Crested Hummingbird in dragon mode

 

Both types of St. John hummingbirds were badly affected by the 2017 hurricanes, when there were no flowers to be found and many birds starved. The Antillean Crested ones have been particularly slow in rebuilding their numbers back up, so we are lucky that there are enough of them to form a troupe. (Actually, I read that a group of hummingbirds is variously called a bouquet, a glittering or a charm.)

 

­I see the larger Green-throated Caribs more often, so I feel closer to them. They are definitely brilliant, charming and energetic.  

 

 

But I have to say I am secretly rooting for the smaller Antillean Crested team. Those flashing green head pieces are hard to resist.