JIM CONRAD'S
NATURALIST NEWSLETTER
Issued from Rancho Regenesis
in the woods near Ek Balam Ruins north of Valladolid in
Yucatán, MÉXICO

July 16, 2017

*****

ROADSIDE GIANT TOAD
Last Sunday on my banana-buying biking trip to Temozón, at the edge of the highway's pavement and sheltering in the shade of overhanging grass, there was the huge, yellowish toad shown at http://www.backyardnature.net/n/17/170716gc.jpg

Different toad species occur in the Yucatan, but from the first it was apparent that this was the Giant Toad, also called the Cane Toad, traditionally designated BUFO MARINUS but nowadays often shifted to its own genus and named Rhinella marina. It was clearly a Giant Toad because of its size, which you can judge better in the picture of him being held in my hand at http://www.backyardnature.net/n/17/170716gd.jpg

In Mexico and North America, there's simply no other toad even approaching being this large.

The toad made no effort to hop away, and when I picked him up he didn't struggle or seem concerned at all. Maybe he'd been stunned by an encounter with a car, though no signs of injury were visible. While I had such a cooperative subject, I took several pictures, including one meant to show the big parotoid gland, which looks like a bean bulging from beneath the skin in the lower, left corner of the picture at http://www.backyardnature.net/n/17/170716gg.jpg

Just last week, showing how to distinguish between an immature Giant Toad and our abundant Gulf Coast Toads, a similar picture was provided emphasizing the Gulf Coast Toad's much relatively small parotoid gland, which you can review at http://www.backyardnature.net/n/17/170709gt.jpg

In that picture, notice how the Gulf Coast Toad's parotoid is about the same size as its eardrum, or "tympanic membrane" behind the eye, while our Giant Toad's parotoid is much larger, as well as shaped different.

I was fascinated by our Giant Toad's front hand, shown at http://www.backyardnature.net/n/17/170716gf.jpg

When I positioned the toad in sunlight for a view of the head, his eyelid-like "nictitating membrane" slid up over the eye, apparently in response to the bright light, as seen at http://www.backyardnature.net/n/17/170716ge.jpg

Nictitating membranes occur not only in amphibians and reptiles but also birds and some mammals. Normally they are whitish or transparent, and serve to protect the eye from dust and to keep it moist.

I was surprised to see a Giant Toad right beside the road with no ponds or ditches nearby, and surprised that the toad's skin was so yellowish. Others I've seen were grayish brown or brown, such as our first one seen in the Yucatan, back in 2005, still online at http://www.backyardnature.net/yucatan/canetoad.jpg

Giant Toads are native to South and Central America, but I'm uncertain as to whether they're native to southern Mexico. They're invasive in much of the world, where they've been introduced to eat unwanted small animals, but often have ended up being pests themselves by eating the wrong things. Besides their normal prey of small rodents, reptiles, other amphibians, birds, and even bats and a range of invertebrates, they also eat plants, dog food, and household refuse.

When I returned to the hut, the first thing done was to wash my hands, because toad skins excrete a milky-white fluid known as bufotoxin, and Giant Toads produce a lot of it. Dogs have been known to die after attacking and chewing on them, and people have died after eating them. In Australia, where Giant Toads are invasive, animals don't know to avoid them, and often die after biting into them. Wikipedia's Giant Toad page says that in Australia they're testing blending bits of toad with a nausea-inducing chemical, in the hope that when native animals eat this bait and suffer a little illness, they'll learn to avoid the toad taste.

The Maya workers here at the ranch looked at my pictures and said they'd never seen this toad, so it's rare, maybe because the environment isn't quite right, or it's just now invading this area.

*****

A CECROPIAS' MYSTERY CATERPILLARS
Twenty-ft-tall cecropia trees grow from the bottom of the pit adjoining the hut I live in. You can see what a cecropia looks like at http://www.backyardnature.net/yucatan/cecropia.htm

What's great about having cecropias in the pit is that their crowns, which usually are too high for a good look, rise to just a little higher than the hut's out-jutting porch. Therefore, the cecropias' big, umbrella-like leaves -- about the size of truck tires -- are a constant presence in my life, and a pleasing one, especially when they're glowing in brilliant tropical sunlight.

The other day I looked over and saw that something had ravaged a couple of a cecropia's big leaves, as shown at http://www.backyardnature.net/n/17/170716cs.jpg

Just below those leaves, BB-size, black pellets gathered atop other ±horizontally growing leaves, seen at http://www.backyardnature.net/n/17/170716ct.jpg

That's caterpillar poop, and it didn't take much looking to find the responsible cecropia-leaf-eating caterpillars, for there were four or five of them, and they were fairly large and black, so very conspicuous on the bottoms of the big, sunlight-charged upper leaves, as seen at http://www.backyardnature.net/n/17/170716cp.jpg

I was tickled with this discovery, because all my life I've seen huge, colorful moths in my field guides identified as Cecropia Moths, but I've never seen one. With these cecropia-leaf-eating caterpillars, maybe at least I was now seeing Cecropia Moth caterpillars. I figured that their identity should be easy to confirm, because not many caterpillar species are armed with such spectacular branched spines, and with such interesting "antlers" as seen in the above shot. Even though I was unable to get closer than about ten feet of the caterpillars (3m), with my telephoto I tried to get as many good views as possible, so volunteer identifier Bea in Ontario would have an easy time of it. A shot focusing on the head end and providing a closer view of the branched spines and "antlers" is shown at http://www.backyardnature.net/n/17/170716cq.jpg

A view of the rear end is at http://www.backyardnature.net/n/17/170716cr.jpg

But, Bea said she didn't think they were Cecropia Moth caterpillar. When I checked the matter myself I saw that late instars of Cecropia Moth caterpillars are mostly bright green -- and mine were so large that they must have been late instars. However, anatomically they were very similar, maybe identical. Therefore, I felt sure we had something very closely related to the Cecropia Moth, and probably in the same genus.

Cecropia Moths belong to the genus Hyalophora, and a search on Hyalophora species documented for the Yucatan indicated no observations of Cecropia Moths. However, one reference listed another species of Hyalophora for the Yucatan, and that species was HYALOPHORA EURYALUS. Disappointingly, all late-instar photos of that species' caterpillars found on the Internet show them as bright green, not black.

In general, Internet pages dealing with plants and animals overwhelmingly treat species of the Temperate Zone, and even if a species extends into the tropics normally that fact is ignored. On the Internet, Hyalophora euryalus is described as a western North America species extending into Baja California, Mexico. However, at http://kuyabeh.com/pdf/listaespecies_ingles.pdf Hyalophora euryalus is listed as a common species in the Yucatan, though no references are given and the website is of unknown authority.

In North America, Hyalophora euryalus is known as the Ceanothus Silkmoth, and is described as feeding on a wide variety of plants.

Though Bea isn't convinced that our black, cecropia-feeding caterpillar is Hyalophora euryalus, and it's worrisome that it's black instead of green, I'm filing it here under that name. Young, small instars of Hyalophora euryalus are blackish, so maybe our tropical individuals simply retain their youthful blackness as later instars. Or maybe the accounts of Hyalophora euryalus occurring in the Yucatan are simply wrong.

Whatever the case, the above pictures and observations should be welcome by any future researcher looking into Hyalophora in the Yucatan.

I'd planned to watch the caterpillars on my neighboring cecropia as they developed, hoping for more insight into their identity. However, one afternoon I looked over to check on them and they were all gone, despite all having been there just an hour or two earlier. The next morning, soon after daybreak, I got a strong hint of what had happened to my caterpillars: A small flock of marauding Green Jays came through and one of those birds landed on one of the mangled cecropia's lower leaf petioles, and twisted his head so he could examine the bottom of the very leaves where earlier the caterpillars had foraged...

*****

SQUASH VINE BORERS
In March I planted some Zucchini seeds, which sprouted vigorously and in just a couple of weeks produced robust plants bearing big, orange, male flowers. Within another week the first female blossoms appeared, bearing miniature zucchini fruits, the ovaries, at their bases. Then armyworms defoliated the plants and ate the stem tips from which future leaves, flowers and fruits were to come. I pulled up the plants.

In June I tried again, after the armyworms had thined out. The same incredibly vigorous, fast development occurred, and then this week just as the female flowers were appearing with their tiny zucchinis at their bases, the plants overnight became pale and wilted. I parted their leaves I saw what's shown at http://www.backyardnature.net/n/17/170716st.jpg

The brownish item at the picture's bottom, center, is the very sick stem. Notice that it's split in places, has holes here and there, and is generally covered with brown, crumbly "frass." Frass is a kind word for caterpillar poop. Seeing all this, I knew my plants were doomed again, for they'd been discovered by Squash Vine Borers, MELITTA CURCURBITAE, occurring in gardens worldwide. To confirm the diagnosis I pulled up a plant and split its main stem down the center, and saw what's shown at http://www.backyardnature.net/n/17/170716sw.jpg

The stem has been hollowed out and is full of brown, crumbly frass. A little more slicing with my penknife and I found two Squash Vine Borer grubs at work, shown at http://www.backyardnature.net/n/17/170716sv.jpg

Those are small, early-instar grubs. A much bigger one not far from metamorphosing is shown at http://www.backyardnature.net/n/17/170716su.jpg

So, the white, grubs shown in the pictures are larvae of a kind of clearwing moth -- one with a mostly reddish body and slender, blackish wings held over the back, so at first glance it looks more like a wasp than a moth. The moth also is unusual because it flies during the day, not at night. When the moths find an appropriate member of the Squash/Pumpkin/Cucumber Family, the Cucurbitaceae, it lays its eggs at the plant's base. About a week later the eggs hatch.

The resulting larvae enter the stems, burrow through their centers, thus blocking the flow of water to the rest of the plant. Larvae feed for four to six weeks, then exit the stems, burrow into the soil, and form a pupa inside a cocoon. In the North, the pupal stage passes through the winter, and then the next summer a clearwing moth emerges from the cocoon, and the cycle starts all over. I'm unsure how the cycle develops in the tropics where there's no winter.

Squash Vine Borers are hard to deal with. Spraying or powdering the vines does no good because the borers don't feed on the plant's surface.

Here's the main advice people give for dealing with them:

I'm guessing that, at least during the rainy season, I won't be growing many Northern-type squash.

*****

SAPRANTHUS FRUIT UPDATE
At http://www.backyardnature.net/mexnat/sapranth.htm we look at a small, annona-like, wild tree growing near the hut, known as Sapranthus. An interesting feature of the Sapranthus's flower is that from a single blossom a cluster of fruit-like items arise.

Normally we think of one fruit deriving from one flower. However, certain individual flowers contain more than one pistils, pistils being the blossom's female parts. These produce "aggregate fruits." Another fruit type results from the maturing pistils of several flowers fusing into one "multiple fruit." Aggregate fruits are produced by blackerries and buttercups, while multiple fruits occur among mulberries and figs. You can access a diagram, pictures and a discussion of aggregate and multiple fruit types at http://www.backyardnature.net/fruits.htm

We've been documenting the Sapranthus's developing fruit -- it's an aggregate fruit -- and you can see what it's become nowadays at http://www.backyardnature.net/n/17/170716sp.jpg

*****

CONCEPT OF CARROT
A garden, is a garden of abstractions.

For, each thing harvested is a physical-world manifestation of an abstract concept that has taken form throughout human history, and still is evolving.

For example, centuries or millennia ago certain humans began paying special notice to a ferny-leafed wildflower with dense, flat-topped clusters of tiny white flowers. It was Daucus carota, which populated much of Europe and southwestern Asia. I'm guessing that it favored mountain slopes because during my traveling days often I saw it looking comfortably at home in alpine meadows. In modern times Daucus carota has invaded North America as the roadside weed known as Queen Anne's Lace, or Wild Carrot.

Probably those first people to take special notice of Daucus carota were grubbing for food. When they dislodged it from the soil, a good smell suffused the air around them. The fragrance issued from the plant's injured taproot, which was so slender and tough that there wasn't much food value to it, but these people were hungry, and ate it, anyway.

A small percentage of those making the discovery -- the most curious and energetic in each community -- asked themselves this: What if this plant were given a little attention -- such as by being watered when it didn't rain, and by removing other plants from around it? In other words, they were conceptualizing a better "carrot," and hypothesizing how they might encourage it to exist. This was the beginning of the carrot concept, and one of many beginnings of the concept of gardening.

Centuries and maybe millennia passed as the hypothesis was proved correct -- and correct not only for Daucus carota but also for many other edible species.

Today both the "carrot" concept and the "gardening" concept are evolving much faster than ever before. For, nowadays horticulturalists are tinkering with genes, and genes define what an organism is. For the first time in history, we're domesticating by manipulating the gene-based instructions for how organisms are assembled.

Moreover, nowadays there's yet another change taking place with even more potential for changing gardening and organisms as we now conceive these concepts.

For, the first gardeners were inventing science and the scientific method. They made field observations, hypothesized, experimented, and the fruits of their successes were shared with mankind. The second change, with even more potential for changing humanity's relationship with Nature than gene manipulations is this: Nowadays knowledge itself and the scientific method are being abandoned by the masses, on ideological grounds.

This week a survey was published showing that in the US most Republicans no longer trust not only the established news media, but also universities, their studies, their scientists. The opposite is true for Democrats.

We all know about the wholesome, beautiful fruits and vegetables the scientific method had brought us. Now we shall see what fruits are born of Trumpism.

*****

Best wishes to all Newsletter readers,

Jim

All previous Newsletters are archived at http://www.backyardnature.net/n/.