Frangipani Caterpillar

St. John Creatures: Frangipani CaterpillarsOne morning, April 10, to be exact, I noticed these little caterpillars all on one branch of my native frangipani tree. Caterpillars are nothing unusual for this tree as probably for as long as this tree has been in existence, which I suspect has been more than 100 years, frangipani caterpillars periodically eat every single leaf on the tree.

Frangipani (Plumaria) TreeI say 100 years because there is a piece of barbed wire sticking out of the trunk, which could only have come from the subsistence farming days when this property was dedicated to raising livestock.

St John Virgin Islands Subsistance FarmingThere’s also a concrete trough nearby to testify to this observation.

I’ve been living here for more than a decade and because of the voracious appetite of the frangipani caterpillars for the frangipani leaf, I’ve only seen the tree flower twice. Normally frangipani trees flower after the onslaught of the caterpillars, but not this one.

Frangipani Caterpillars But the caterpillars I saw that Friday morning were different than the large black, yellow striped caterpillars that I’d been accustomed to finding all over the tree munching on the leaves. They were similar, but much smaller, not nearly as colorful and all of them were congregated on one branch. I was fairly sure that they were baby frangipani caterpillars, but I was intrigued. Why were they only on one branch and where did they come from?

St. John Fauna: CaterpillarsAs I’ve been fascinated with these creatures, I decided to do a little study. I photographed them that morning and again the next day, when they began to look more like the frangipani caterpillars I was used to, although smaller and still on that single branch.

HornwormThe frangipani caterpillar is also called frangipani hornworm because of the black hornlike feature on its posterior. This caterpillar also seems to be in the process of defecating, thus fertilizing the tree as it drops to the ground.

In a few days the caterpillars resembled those I was used to seeing on the tree. They spread out and got big and fat and colorful and within a little more than two weeks had consumed every leaf on the tree. This time I was ready for them. I wanted to see what happened to them next. Where they go?

St. John Virgin Islands Environment: Leaf LitterThis morning, with every scrap of leaf gone, the caterpillars crawled  down the tree trunk and I followed them. Some crawled one way and others went in the opposite direction. Eventually they found area where old leaves were piled up and composting. They burrowed into the leaves and disappeared from my sight.

Ifrangipani caterpillar pupa waited about 30 minutes and removed the leaves from where I last saw the caterpillar, where I found this similar-looking creature. It appeared curled up, stiff and shrunken, but moved to burrow further into the soil when exposed.

From what I’ve read about the frangipani caterpillar, this might be the beginning of the pupa stage from which eventually emerges the Tetrio or Giant Gray Sphinx moth and then again it might be a different creature altogether.

size difference
Full-sized caterpillar placed next to what I believe to be the pupa stage

On further inspection of the leaf litter, I found the frangipani caterpillar. The creature I thought might be the pupa, is, apparently a yellow-banded millepede.

I’m still looking to find the pupa that according to looks like this: frangipani caterpillar pupa



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