Frangipani Caterpillars, Aposematism and Mangrove Cuckoos

Cultivated Hawaiian Frangipani
native frangipani
Native Frangipani

I have this native frangipani tree growing right below my deck. The tree has been there quite some time evidenced by a rusted piece of wire fencing that had grown into the trunk and now sticks out on both sides of the tree, indicating that this was a mature tree when Chocolate Hole was still used for grazing animals. My guess, seventy to a hundred years old.

But why not? Native frangipanis grow and flower in the most inhospitable environments on St. John. They grow slowly, recover quickly from windstorm damage and as far as I know, only have one significant enemy outside of people.

frangipani caterpillar

I’ve watched this tree since I’ve been living here waiting for it to produce bouquets of sweet-smelling, white flowers, on the top branches of the frangipani tree, which could be seen directly at eye level by someone standing on the deck. But, alas, so far this has never happened.Every so often, especially in the spring the leaves on the tree grow back lush and green and the flowers begin to bloom. That’s when the attack begins, because along comes this army of caterpillars that quickly devour every last flower and leaf on the tree. The frangipani survives anyway and the tree makes new leaves and new flowers whereupon arrive the caterpillars and the cycle begins once again, and so on.


The culprit is the frangipani caterpillar, a brightly colored fat black bug with iridescent yellow stripes and a red head and red legs. It’s called a frangipani caterpillar because it only eats the leaves and flowers of the  frangipani tree, although I have seen them also go to work on alamandas and even the highly toxic oleander.

The caterpillars have voracious appetite. They start off relatively small, but get big and fat fast. They can eat an entire leaf in a few minutes so it’s not long before there’s so many caterpillars that they look like black and yellow flowers and not long after that there’s nothing left on the tree but bare branches, the caterpillars going off to change into moths somewhere.

This year I intend to go to was against these bugs.

So far I have been winning the preliminary battles easily without even having to resort to chemical warfare. The tree is not that tall and I’m able to knock them down using that handy multipurpose St. John tool, a forked stick.

Once they’re down, I’m faced with a moral dilemma, what to do with them.

Kill them?

Easy enough, they don’t run very fast.

But I do happen to be impressed by those bright beautiful colors, and the thought of squishing them underfoot with their guts just about bursting with green, gushy, chewed-up frangipani leaves seems like it may be somewhat, how should I put this, disgusting.

So far, there haven’t been that many caterpillars to deal with, so I simply bring them somewhere else, away from the tree, in hopes that they’ll get lost or and not be able to find their way back. They will, however, have all the time they want, because they have no natural enemies.

Birds and any other predators that normally would eat caterpillars stay away from the Frangipani Caterpillar, whose guts are oozing with poisonous frangipani sap, warned by the bright colors. This defense mechanism is called “Aposematism,” a warning, usually in the form of bright vibrant colors, to a potential predator that there would be some problem associated with going after that particular prey.

mangrove cuckoo

There is an exception to every rule and this particular exception takes the form of the fairly rare mangrove cuckoo.

The cuckoo gets around the poisonous guts by slapping the caterpillar against the trunk of a tree until there’s no guts left. Having accomplished that culinary preparation, the cuckoo will dine on the frangipani caterpillar, whose aposematism didn’t quite do the trick.

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9 thoughts on “Frangipani Caterpillars, Aposematism and Mangrove Cuckoos”

  1. Hey Gerald,

    You are also missing the fact that the frangipani caterpillars are in a symbiotic relationship with the frangipani. The plant feeds the caterpillars and the caterpillars feed the plant with their feces (which you undoubtedly noticed).

    This is one of the best fertilizers you can give the frangipani and no matter how much you let the caterpillars eat they won’t kill the plant, they only eat mature growth and leave the buds alone.

    Let them do their thing and the plant will quick come back stronger than ever.

  2. Hi Randy,
    Except that the tree never flowers if the caterpillars are left to their own devices.

  3. I let the Frangipani caterpillar eat my leaves off every season, and the plant ALWAYS springs back with leaves and blossoms. Last week the 5 year old bush was picked clean, but flowers left alone, and in fact the new leaves started to appear even before the caterpillars had finished with all of the old.
    This August 2011 however, was the biggest influx of the F.C. that I remember in 13 years. In fact, when they finished off the Frangipani, they moved on to my yellow Allamanda just like above article says. But they were everywhere around my house, and the quantity of poop around each bush was really obvious. Would love to see the mangrove cuckoo in action preparing them to eat…I just get Thrushies.

  4. The Frangipani will flower beautifully even when eaten clean by caterpillars. In no time the bush is back healthy after the caterpillar attack. I have lived in Antigua for 40 years and the Island is full of blooming Frangipanis. Right now we are in the middle of a very active caterpillar season, but I know in ashort while my bushes are as good as new.


  5. It is part of nature for the caterpillars to eat this tree hense frangipani tree/frangipani caterpillar. Why do you find it necessary to remove them from the tree?

  6. The Frangipani caterpillar should be left alone to do it’s thing. It is a symbiotic relationship that the Frangipani and caterpillar enjoy. In fact, the caterpillar helps to promote bloom on your tree … so just leave them alone!

    Frangipanis are subject to many diseases that can damage and even kill your tree. The caterpillar helps remove some of those diseases (other than rust) by removing old growth and forcing new growth. It is cyclical and will recur every year. In 20 years of living on Tortola and with 5 very large (over 20′) and quite healthy Frangipanis that bloom considtently, I have yet to see a tree destroyed by the Frangipani caterpillar.

    Leave them alone and thank them for helping to keep your trees healthy! They are an integral part of mother nature’s grand plan. Spraying them is basically one of the dumbest things you could possibly do.

  7. Been leaving the caterpillars alone now for almost two years now and not a single flower has had the chance to develop. I realize that this is not the generally the case as I have other trees that enjoy the traditional symbiotic relationship with the caterpillar, but not this tree. As soon as the first leaves or buds develop, the caterpillars make short work of them.

  8. I hear you gerald. I have the same problem with two frangipani trees which happen to grow next to my front door. It is just not nice to walk under branches laden with worms and poop all around. There is almost never a chance for flowers to bloom and for the trees to look beautiful without intervention, which I don’t like. Maybe i should just cut the trees and plant something else.

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