JIM CONRAD'S
NATURALIST NEWSLETTER
Issued from Mayan Beach Garden Inn 20 kms north of Mahahual
on the Yucatán Peninsula's eastern coast just north of the Belize border,
in the state of Quintana Roo, MÉXICO
(N18°53'16.36', W87°38'27" )

September 11,  2011

"MIGRATING BUTTERFLIES"
This week dark butterflies began passing, following the beach southward. They flew so fast I couldn't see much about them, other than that they were blackish, had tails like swallowtail butterflies, and they were the right size for being swallowtails. I thought of them as "migrating swallowtail butterflies."

Then during Thursday morning's post-storm drizzle, the Tropical Almond tree outside my window turned up with maybe 20 of these migrants flitting among branches, taking nectar from flowers and sometimes settling on leaf undersides. You can see one leaf-sheltering at http://www.backyardnature.net/n/11/110911mo.jpg.

Here and there the migrants clustered, as shown at http://www.backyardnature.net/n/11/110911mn.jpg.

The moment these images appeared on my computer screen I knew that they weren't swallowtail butterflies, if only because their bodies were too thick. Maybe they were skippers. But volunteer identifier Bea in Ontario is the specialist there, so I sent the pictures to her. At first she was nonplussed as I, but by Friday morning she had it figured out: These were not swallowtails, not skippers, NOT EVEN BUTTERFLIES!

They're Sunset Moths, sometimes called Urania Swallowtail Moths or Green Page Moths. They're URANIA FULGENS. And, once you have the name of something, then you can look it up and get its story. So...

Several species of Urania Swallowtail Moths exist, but this one, Urania fulgens, occurs from southern Texas south to Bolivia. And these moths are famous for their majestic migrations.

The caterpillars of Urania fulgens feed on a woody vine, or liana, in the Euphorbia Family, Omphalea diandra, sometimes called Jamaica Navelspurge. Jamaica Navelspurge's vegetative parts are poisonous to many or most higher animals, but the fruits are edible for humans if the poisonous embryo is removed. Thing is, the vine doesn't grow in the Yucatán, or even in Belize to our south. It's found in the Caribbean and south through tropical South America.

So, maybe the moths passing this week were returning to where they spent their caterpillar days -- where Jamaica Navelspurge grows -- after spending summer in the Yucatán just sipping nectar and surviving. Or maybe they're in transit from Jamaica or Cuba, south to Costa Rica, following the Yucatán coast from one navelspurge area to another.

Marcia says that some years she's seen large numbers of Sunset Moths roosting here overnight on Tropical Almond trees. On the Internet, entomologist Neal Smith reports the passage of millions of them through the Panama Canal Zone in the fall of 1969, flying an estimated 60-100 miles each day (100-160km). Smith's interesting paper is available online in PDF format at http://academic.uprm.edu/publications/cjs/VOL12/P045-058.PDF.

*****

FOAMFROG
At 8AM in full sunlight and in the middle of the semi-abandoned asphalt road across the mangroves I biked past the unblinking, 1.5-inch long (37mm) frog seen at http://www.backyardnature.net/n/11/110911ff.jpg.

Here it's unusual to see any kind of frog other than the Gulf Coast Toad, so I was tickled when I turned the bike around, went back, and the frog was still there. Though its skin was warty, it wasn't a toad with poison-secreting parotoid glands behind the eyes. Its long toes lacked roundish tips helping it stick to vertical surfaces, so it wasn't a treefrog. It seemed to be something completely different from what I normally see, and maybe with that distinctive white stripe above the mouth I might even identify it.

So, it's the White-lipped Foamfrog, also variously called the Mexican White-lipped Frog, American White-lipped Frog and White-lipped Whistling Frog. It's LEPTODACTYLUS LABIALIS. It's a species occurring in a variety of habitats, including disturbed areas, from southwestern Texas (where it's listed as Threatened) south to Panama.

The name foamfrog alludes to how males use their hind feet to whip the bright yellow eggs and jelly capsules surrounding them, as well as his seminal fluid, into a foamy, meringuelike nest. In Amphibians and Reptiles of Northern Guatemala, the Yucatán, and Belize, Jonathan Campbell writes that the nests are usually placed in mud cavities a few feet beyond the water, during periods of increasing rains. Eventually rising water covers the nests.

Since this is the beginning of the rainiest part of our rainy season and the mangroves' waters grow deeper every week, I'm guessing that this female (large tympanum and rounded instead of pointed snout) was out looking for good egg-laying territory, maybe having been driven from where the water was getting too deep. The road she was on had flooded mangrove on both sides. The species is mostly nocturnal.

There's another shot of this frog's head, one just meant for looking at and admiring, at http://www.backyardnature.net/n/11/110911fg.jpg.

*****

GREAT BLUE HERON OFFSHORE
Northern Birders are familiar with Great Blue Herons, the largest of dark herons and common in North America from coast to coast. They're common in Mexico, too, stalking prey in both fresh and saltwater, though mostly they're only winter visitors. Here I haven't seen one all summer, so it was a nice surprise when one showed up wading in Turtleweed shallows a stone's throw from the beach. He wouldn't let me get close enough for a picture of him wading, but he was curious as well as cautious, so instead of flying away he flew by me, and I got the picture of him on the downbeat at http://www.backyardnature.net/n/11/110911gb.jpg.

Howell reports Great Blues as present in the Yucatán from September through April, plus there's a disjunct breeding colony in Sian Ka'an Biosphere Reserve just to our north.

*****

BIVALVE/CLAMSHELL/SCALLOP/PECTEN...
On the beach just beyond the waves I found a 2-inch- wide (5cm) seashell, both sides of which are shown at http://www.backyardnature.net/n/11/110911sh.jpg.

My first thought was how pretty the brightly orange-red shell looked lying atop the white sand, ornamented with those intricate and mysterious squiggles covering the shell's interior side, and those curious, toothlike growths atop the shell around the edges. But my next thought was that even after four solid months of beachcombing I remain so ignorant that I couldn't answer a child's simplest questions about what kind of shell it was.

I knew that the animal producing it was a bivalve, but that name applies to the whole "class" Bivalvia, which are mollusks with bodies protected by two hinged shells. Calling it a bivalve is like saying something is a bird (class Aves) or mammal (class Mammalia); it's not saying much.

The term "scallop" popped into mind. Scallops are marine bivalves of the Pecten Family, the Pectinidae. Scallops are eaten and often have brightly colored shells with radiating wavy patterns like ours. The shell design used by Shell Oil is based on a seashell known as the Giant Scallop, whose technical name is Pecten maximus. So, scallops and pectens are pretty much the same thing, and our shell looked a bit like the Shell Oil one.

On that basis alone I wasted several hours Googling for pictures of scallop and pecten shells looking like ours. I found shells very similar to ours, but none exactly the same.

And then along came volunteer identifier Bea in Ontario who declared our shell an oyster shell!

Until now I've visualized oyster shells as flattish, irregularly formed, mottled, brown and white, rather unkempt-looking things not at all like our shell. But Bea introduced me to the concept of the "thorny oyster" of the genus Spondylus. Lots of spondylus shells are brightly colored and ornamented with radiating ridges, bumps and spines, just like ours.

I'd run into that word "spondylus" before. As a kid I saw National Geographic pictures of Polynesians wearing spondylus shell necklaces, never dreaming that one day I'd find such shells myself. But now I read that people in many places have been picking up spondylus shells for a long time. Archaeological evidence indicates that as far back as 5,000 years ago Neolithic Europeans were trading shells of Spondylus gaederopus for making bangles and other ornaments.

There are lots of species of the genus Spondylus. Bea found a whole page of different species showcased at http://www.nmr-pics.nl/Spondylidae/album/.

I'm thinking that the Digitate Thorny Oyster, SPONDYLUS ICTERICUS, distributed in the western Atlantic from Florida and Bermuda to Brazil, comes the closest to ours. But that's the guess of a real seashell-identifying amateur.

*****

WORM TUBE ABSTRACTIONS
In the above picture of the underside of our spondylus shell, at the left, you saw a bunch of squiggly lines. Up close the squiggles are more interesting, as seen at http://www.backyardnature.net/n/11/110911wt.jpg.

In that picture, notice how each squiggle begins at a tiny point, then expands toward the other end. Also, at least two kinds of squiggles are apparent, one constituting a hollow, white tube, the other looking like a tiny eel's skeleton with backbone and ribs.

On the Internet I found "Jessica's Nature Blog" with a whole page about such squiggles on oyster shells. Jessica is an ecologist in England. Her squiggles look like the wandering, solid tubes on our shell, which she calls calcareous worm tubes, and says that they're made by small marine worms of the Serpulidae family. I wrote to Jessica asking about the "eel skeleton."

She'd not seen anything like that in European waters, but she had books saying that "Serpulid worm tubes can be quite complex, look partially segmented, and have projecting features" like our "eel skeleton." Jessica's interesting "Oyster Variations" page is here.

Her page called "Two thousand years of eating oysters in the UK: an archaeological perspective" is here.

So, those squiggles on our spondylus shell are calcareous worm tubes created by "serpulid worm encrusters." "Calcareous" means that chemically the shells are like limestone, mostly composed of calcium carbonate. Other kinds of tube worms create calcareous tubes that wash onto beaches unattached to anything, looking like fossilized macaroni. The Serpulidae family belongs to the "class" of Polychaeta and the "phylum" of Annelida, so serpulid worms can more generally be referred to as both polychaetes and annelids, or segmented worms.

Tubes worms filter the water around them for food. When alarmed they retract into their tubes and close the tubes with little doorlike scales called operculums. On our shell we can see that they grow as they feed, adding length to their shells.

*****

YELLOW-FLOWERED VINE WITHOUT A GOOD NAME
Several times daily I duck below a luxurious mass of densely tangling vine overgrowing the beam above the gate leading to the kitchen. The vine bears large, yellow, trumpet-shaped flowers. You can see it all at http://www.backyardnature.net/n/11/110911yv.jpg.

A close-up of the 2.5-inch long (6cm) flowers is at http://www.backyardnature.net/n/11/110911yw.jpg.

There's a commonly planted, similarly robust vine with similarly trumpet-shaped, yellow flowers planted throughout the world's tropics (next section), often called the Golden Trumpet Vine. The kitchen gate vine is something else. The evidence for that is shown at http://www.backyardnature.net/n/11/110911yx.jpg.

That's a view down the throat of one of this vine's flowers. The corolla tube is yellow with narrow, red lines radiating from the center, exactly as with the Golden Trumpet Vine, but what are those yellow, curly things lying on the throat's floor? In the next section we'll see that they're completely missing in Golden Trumpet Vine flowers.

Each of those five curly things arises atop one of five anthers. They are "anther appendages" and I'm guessing that they provide footholds for visiting pollinators. Like the red lines, the appendages also serve as nectar guides pointing toward access to nectar at the flower's base. In a blossom's longitudinal section you can see how the anthers join like a tepee over the blunt stigma head, with the curly appendages arising from their tips, at http://www.backyardnature.net/n/11/110911yy.jpg.

The vine is PENTALINON LUTEUM, and if you need a commonly accepted English name you're out of luck. Lots of names can be found for it but none seems more used than any other. There's Yellow Mandevilla (though it's not a Mandevilla), Yellow Dipladenia (not a Diplandenia), Wild Allamanda (not an Allamanda), Lice Bush, Wild Wist, and then there's the USDA's inlikely Hammock Viper's-tail.

The species is mostly Caribbean in distribution. I see it growing wild at the edges of mangroves here but can't decide whether the plants are natural, or have been swept there from gringo beach properties rearranged by hurricane storm surges.

As is often the case with members of the Dogbane Family, all parts of Pentalinon luteum are poisonous if ingested, and even handling can cause skin irritation.

*****

GOLDEN TRUMPET VINE
Across the walkway from the Pentalinon luteum the similar-looking but much more commonly grown Golden Trumpet vine, ALLAMANDA CATHARTICA, also is flowering. Its slightly larger (4-inch long, 10cm), yellow flowers with slender reddish throat veins are shown at http://www.backyardnature.net/n/11/110911al.jpg.

Notice that Golden Trumpet normally bears three or four leaves per stem node to Pentalinon luteum's two. Another difference is that when you look down the Golden Trumpet flower's throat you see what's at http://www.backyardnature.net/n/11/110911am.jpg.

The yellow corolla wall with red lines radiating from the center is the same as with Pentalinon luteum, but that species' curly anther appendages are missing. A longitudinal section of a blossom's mouth is shown at http://www.backyardnature.net/n/11/110911an.jpg.

There you can see how the nearly stalkless, arrowhead-shaped anthers meet above the greenish, rounded stigma head forming a tepee. Also, stiff, white hairs point upwards above the stigma head, and downwards below the stigma. Pollinators pass through this well barricaded zone by passing between the hair tufts. The tufts are situated so as to oblige pollinators entering the flower to deposit pollen from other flowers onto this blossom's stigma head, but when leaving, to carry pollen from this flower's anthers to other flowers.

Golden Trumpet is native to Brazil but because of its prettiness is planted throughout the world's tropics. Several cultivars have been produced, some famed for their fragrances.

As with many members of the Dogbane Family to which Golden Trumpet belongs, the Apocynaceae, the plant's milky sap is poisonous. As suggested by the species name, Allamanda cathartica, all parts are cathartic. Cathartics purge the bowels.

*****

PREDAWN RAIN ON THE YUCATÁN'S EASTERN COAST
As we approach the peak of this year's rainy season's raininess, I'm understanding how it works here on the Yucatán Peninsula's eastern coast. It's very different from what happens in the peninsula's interior, where the rainy season is expressed in terms of heavy, often violent afternoon thunderstorms. In the interior, mornings begin clear, by midmorning it's clouding up, then by mid afternoon storms break out here and there, maybe right over you. The peak comes in September and October. You can see a typical mid-afternoon view from our northern rocky point toward the south, showing storm clouds building over land but not over sea, at http://www.backyardnature.net/n/11/110911wx.jpg.

Here on the peninsula's eastern coast prevailing winds blow from off the ocean in the east, so those interior storms that form to our west just drift farther westward. During the interior's rainy afternoons, storms don't form over us or the water because it's much cooler on and beside the ocean, and for storms to form you need stark temperature differences. You need warm surface air to bubble up through cooler air, to high altitudes.

For the last two or three months, even as afternoon rains drenched the interior, for the most part it's stayed dry here on the coast. Rains mostly came when tropical depressions or "areas of disturbed weather" formed in the Caribbean, then wandered over us, sometimes dumping several inches of rain over a period of days.

Lately a new trend has begun and Marcia says it'll develop more fully until things really get soggy in October. That is, right before dawn, storms or showers form out over the water and drift over us. What's happening is that during the night air over the water cools dramatically, but the ocean water remains warm - - about 86°F (30°C) off our coast.

Therefore, right before dawn, air immediately over the warm water starts bubbling up through the night-cooled air above it, until it reaches an altitude where condensation occurs. Then rain falls as the cloud drifts over us, sometimes lots of rain, with lightning and thunder, just about when I'm jogging.

*****

ON NOT SAYING ANYTHING
The Tao Te Ching says, more or less, that the master teacher says nothing. When I first read that back in the 60s I couldn't imagine what Lao Tzu was trying to get at. If a great teacher has insights into the world's problems, shouldn't he or she share them by speaking up?

During these months of horizon-gazing on the beach, every day online radio has enabled me to listen to Public Radio in the US as the rest of the world conducted its wars and scandals, its economic summits and political campaigns. I'm left noticing that after months of saying nothing, the sea remains as powerful, poetic and inspirational as ever, while the verbose world beyond hasn't improved at all.

Praised be the wave, how it comes and goes, but says not a word.

And yet, here on the beach with sea-breezes and salt spray, ocean sounds and odors and hidden worlds beneath and beyond the waves, it seems to me that certain words are almost impossible NOT to say:

"Oh, look at that pretty thing," one can say without contributing to the muddle, the clutter, the miserable discomposure of things. Or, "Oh, and how interesting!" and "Oh, and how good it all is!"

*****

Best wishes to all Newsletter readers,

Jim

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