Excerpts from Jim Conrad's
NATURALIST NEWSLETTER

from the July 16, 2017 Newsletter issued from Rancho Regensis north of Valladolid, Yucatán, MÉXICO
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 below:

Cecropia leaves damaged by Hyalophora caterpillars

Just below those leaves, BB-size, black pellets gathered atop other ±horizontally growing leaves, seen below:

Feces of Hyalophora caterpillars on Cecropia leaves

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 below:

cf. Hyalophora euryalus caterpillar on Cecropia leaf

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 below:

cf. Hyalophora euryalus caterpillar on Cecropia leaf

A view of the rear end appears below:

cf. Hyalophora euryalus caterpillar, rear end, on Cecropia leaf

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...