August 6, 2017

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BIG CATERPILLAR CLUSTER
I was showing some German guests around the rancho when we came upon something amazing. You can see one of the guests standing next to the discovery at https://www.backyardnature.net/n/17/170806ca.jpg

Notice the dark smudge on the tree trunk's side, extending from the ground to the top of the picture. A closer-up view of the smudge is at https://www.backyardnature.net/n/17/170806cb.jpg

They're caterpillars. We've documented large caterpillars clustering on tree trunks before, at Chichén Itzá. You can see that those were somewhat different, though, at https://www.backyardnature.net/yucatan/papilio.htm

Our present caterpillars are much more colorful. Just look at a close-up of their mid-sections, a psychedelic picture worth framing, at https://www.backyardnature.net/n/17/170806cc.jpg

Another view, of a head from above, is at https://www.backyardnature.net/n/17/170806cd.jpg

The clustering caterpillars previously seen at Chichén Itzá were larvae of swallowtail butterflies, so I assumed that these also where swallowtail larvae. However, searching for images of such caterpillars among the swallowtails turned up nothing. Then I tried adding to the keywords the name of the tree on which our rancho caterpillars were feeding, which was Guazuma ulmifolia, a member of the Hibiscus Family, the Malvaceae. This information turned up good matches.

Our rancho's gaudy, clustering caterpillars are larvae of the Giant Silk Moth ARSENURA ARMIDA, distributed from Mexico to Ecuador and Brazil in South America. During the day the larvae rest on tree trunks, where they depend on their warning coloration, or "aposematim," to keep predators away from them. They feed at night, then return to their resting spot at dawn by following scent, or pheromone, trails. After the larva's 4th instar, or growth stage, it descends to the ground, digs a hole , crawls into it, and pupates. The adult that emerges from the pupa is a large, brown moth with a wingspan of 10-12cm (4inches).

One feature of the caterpillar's feeding behavior is especially interesting and hard-to-explain: During early instars the caterpillars cluster in separate patches and forage nomadically. As they age, however, they shift to a central foraging location. A more detailed discussion of this behavior and the theories about it is provided on the species' Wikipedia page at https://en.wikipedia.org/wiki/Arsenura_armida

Our caterpillars are older, late instar ones and their central foraging and resting location is the Guazuma ulmifolia whose trunk is shown in the picture. An idea of how much the caterpillars feed is provided by the mound of caterpillar poop at the tree's base, shown at https://www.backyardnature.net/n/17/170806ce.jpg

Guazuma ulmifolia, a member of the Hibiscus Family, is one of the most common trees in our area, and I'd guess that the one in the picture has had about one-fifth of its leaves stripped by the caterpillars. You can see a typically caterpillar-munched-on branch at https://www.backyardnature.net/n/17/170806cf.jpg

Though large, late instars of the caterpillar are so toxic that they've been known to kill trogon nestlings when fed to them, the smaller, early instars traditionally have been eaten by people in some places, such as in Mexico's Veracruz state, where they are cooked. The larvae also have been preserved in vinegar, which is reported to impart to them the taste of herring.

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DEATH'S HEAD BEHIND THE REFRIGERATOR
Despite having no electricity at the rancho, several refrigerators are scattered about, all broken down and all used for storage. They're just the thing were rodents and insects get into everything. The hut I live in has two, one outside for storing food and another inside for clothing.

This week when I was sweeping the hut I nudged the clothes refrigerator a little away from the wall to get dust behind it, and saw something strange sticking to the wall, something primitive looking, like you'd expect to find fossilized in stone. I grabbed a flashlight, focused it on the object, poked my camera into the crack, and took the picture shown at https://www.backyardnature.net/n/17/170806cr.jpg

I can't focus my eyes at certain distances so not until I reviewed the image in the camera did I notice that it bore spiny legs and slender antennae. This encouraged me to shift to the refrigerator's other side, focus the flashlight from a new angle, and slip in the camera for a picture showing antennae arising from a head tucked beneath a top shell, shown at https://www.backyardnature.net/n/17/170806cs.jpg

At this point I remembered that I'd seen something like this before, back in 2010 when a similar one turned up one night inside my mosquito net, at Chichén Itzá. That one was identified as an immature stage of the True Death's Head Cockroach, BLABERUS CRANIIFER, distributed from the southern US through Mexico to Belize, and in the Caribbean, and whose page illustrating the big adult is at https://www.backyardnature.net/yucatan/deadhead.htm

Once I realized what the refrigerator visitor was I plucked him from the wall, and took him outside for a portrait, shown at https://www.backyardnature.net/n/17/170806ct.jpg

The adult Death's Head has wings and can glide for short distances but can't fly. Wingless juveniles burrow. The name Death's Head come from the markings atop its head area, the pronotum, shown on our page.

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MOBILE & IMMOBILE NUTRIENTS
At https://www.backyardnature.net/mexnat/ackee.htm you are introduced to the Ackee tree, famous for producing a highly edible food much used in Jamaica, and found planted along a street in Mérida awhile back. My friend Eric provided me with seeds, the seeds germinated, I planted them months ago, and then after an initial spurt of fast development, the plants almost stopped growing and began looking malnourished. Now all my seedlings have died except one, and it doesn't look so healthy. You can see it at https://www.backyardnature.net/n/17/170806ak.jpg

Two things to notice: First, the lower leaflets display "interveinal chlorosus." Chlorosus is when vegetation fades from its normal deep green color, turning pale and somewhat yellowish. The term "interveinal" just means "between the veins," so the interveinal chlorosus in our plant is shown by the network of dark green veins in otherwise yellowish leaflets.

The second thing to notice is that the lower, older leaflets are displaying interveinal chlorosus, but the upper, newer ones are more evenly darker green.

These two facts were very important when I began to diagnose my Ackee seedling's problems. My diagnoses was based on the fact that some plant nutrients are mobile while others are immobile. Helping me along was a web document I freely downloaded in PDF format, from the University of New Hampshire, at http://e-gro.org/14_images/webinars/11_19_13_nutrition.pdf

Another web page helping out, sponsored by Michigan State University page, wa at http://msue.anr.msu.edu/news/knowing_nutrient_mobility_is_helpful_in_diagnosing_plant_nutrient_deficienc

First of all, 17 elements are recognized as vital to plant growth. Of these, 14 must be dissolved in soil water in order to be taken up by rootd. Of these 14, three are used in relatively large quantities, and are considered "primary plant nutrients." They are: Nitrogen, Phosphorous, and Potassium.

Three more elements are considered "secondary nutrients": Calcium, Magnesium and Sulfur.

The eight remaining elements are "micronutrients," needed in small quantities, but nonetheless they are essential. They are Boron, Chlorine, Copper, Iron, Manganese, Molybdenum, Nickel and Zinc.

Notice that in our context we're using the terms "elements" and "nutrients" interchangeably.

Some of these 17 elements can be moved around inside the plant, and are considered mobile; others have to stay where they are originally placed. If a growing plant is suffering a nutrient deficiency, it wants to scavenge its limited supply of that element from old leaves and sent to its more efficiently photosynthesizing new growth, but it can move only its mobile nutrients.

Our Ackee seedling has shifted mobile nutrients from its older, lower leaves, causing interveinal chlorosus there, to produce its darker, greener, newer upper leaves. Since our little Ackee has moved its nutrients from below to above, and this caused the lower leaves' interveinal chlorosus, the Ackee is having problems with one or more mobile nutrients.

The mobile nutrients are Nitrogen, Phosphorus, Potassium, Magnesium, Chlorine and Molybdenum.

Nitrogen deficiency normally causes a uniform chlorosus, not chlorosus just between the veins. Phosphorus deficiency normally results in deep green foliage, not chlorosus. Potassium deficiency produces a brief chlorosus at the tip and margins of old leaves. Magnesium deficiency causes interveinal chlorosus on older leaves...

So, we may have Magnesium deficiency. A couple of other nutrients, Sulfur and Molybdenum, are partially mobile. However, Sulfur causes a general chlorosus and death (necrosis) of young leaves, and Molybdenum causes a narrow chlorotic band around the leaf margin, developing into necrosis, so it's neither of those.

We're led to Magnesium but there's another consideration. Nutrient availability can be affected by such things as a low pH (acid soil), low temperatures, water-clogged soil, and soil compaction.

Of these, in our case soil compaction is a real possibility, since our limestone-based, clayey soil compacts very easily.

I read that the best way to treat garden plants showing Magnesium deficiency is to spray the leaves with a solution containing Epsom salts. Applying compost to soil reduces the possibilities of Magnesium deficiency.

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PAPAW'S WHISPERS
My Papaw Conrad -- whom my father called Pap, and others Moda or Mody, and on paper was Morton Joseph -- was a tallish, fat, western-Kentucky farmer who, except at Christmas, wore blue bib coveralls. He came to mind this week as I was reading on my Kindle, looked up for a moment and found the dogs wagging their tails and grinning at me.

I'd been whispering my thoughts again, and the dogs figured I was talking to them. Papaw Conrad whispered his thoughts so clearly that sometimes it was embarrassing to hear them. The Conrad family's whispering gene skipped my father but resurfaced in me.

I like the idea of manifesting part of Papaw Conrad. He taught me my first tree, the Silver Maple beside his porch, though he called it Water Maple, the local name, thus also providing my first lesson on the vagaries of common names.

Gene-predisposed behaviors and manners of thinking and feeling, passed down through the generations, are just as real as inherited skin color, nose length, intelligence and general disposition. Inherited, gene-based features such as unconscious whispering are like ghosts that come and go, sometimes withdrawing for generations, only to resurface when least expected.

I doubt that there's a gene just for out-of-control whispering, but there well may be one for vividness of imagination, and maybe another for leakages between thoughts and a hair-trigger tongue.

If that's so, then surely with every attribute such as "vividness of imagination" and "susceptibility to leakages between brain and tongue," there must be a gradient. A person is endowed with more or less vivid imagination than average, and more or less vulnerability to leakages between brain and tongue.

Once you start thinking like this, it's almost like thinking of humans as machines with onboard computers. Our appearances, behaviors, and what seem to us our feelings and thoughts, it would seem, all manifest information encoded in our DNA, information that results in our being predisposed toward particular states of being.

I do think like that. Moreover, I find the insight encouraging, and liberating.

It's encouraging because if we are all programmed, then we must be programmed for some specific end. Is the end "good" or "bad"? Looking around at the Earth's and the Universe's smooth-working, awe-inspiring gorgeousness, I'm encouraged to think that our human programming probably has been pursued with the same benevolence as all the rest of the Universe.

The insight is liberating because in it I find confirmation that it's OK for me to live according to my personal predispositions instead of the dictates of society -- society which too often is based on fossilized social structures. Of all entities known and imaginable in the Universe, is there anyone or anything more appropriate for giving me guidance on how I should live my life than the Universal Programmer, who informs me how She wants me to live by way of Her own programming written in my genes?

Of course this way of seeing things doesn't give me permission to do whatever I feel like anytime I want. Like my distant hunter-gatherer ancestors, I'm programmed to crave sweet and greasy, high-calorie foods. However, also I've been programmed at a higher level to use my brains to choose which of such elemental predispositions I should yield to, or avoid.

Before committing the last paragraph to my computer's RAM memory, I glanced up from the screen and found the dogs wagging their tails and grinning at me. Then I heard myself laughing. I can't think of a better signal from the Universal Programmer saying that I'm on the right track thinking like this.

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Best wishes to all Newsletter readers,

Jim

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