Curious about white butterflies

On recent trips to East End, I have noticed great numbers of white butterflies, many of which unfortunately wind up hitting my windscreen. Would you be able to find out what they are, why there are so many, is there a specific time of year that they appear and does driving into the swarms significantly impact the population?

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Auntie’s answer: Not only was I able to find out the information you requested but I also was given a very interesting lesson on the butterflies in question. Fred Burton of the Department of Environment informed me that the Great Southern White butterfly, Aschia monuste, naturally cycles through large population explosions in Cayman.

He said that the females lay eggs on a native vine, Capparis flexuosa, known locally as ‘Raw-bones’ because its seeds, which are ivory white, emerge from pods with bright red pulp. The caterpillars feed on the Raw-bones leaves.

As for the great numbers of these butterflies that seem everywhere these days, Mr Burton very descriptively explained, “During population booms there are places you can literally hear the rain of caterpillar droppings because there are so many of them gobbling up the Raw-bones leaves at the same time. Then they all emerge and there are thousands of white butterflies everywhere. Typically, this happens in the summer months, but exact timing varies enormously, does not happen on every island in every year, and is not usually synchronised in Grand Cayman and the Sister Isles.”

But you don’t have to worry that you are wreaking havoc on this species as you drive down the road. That is left to other forces. “Mortality of the butterflies is very high naturally (birds love to eat them) so the percentage that get hammered by cars doesn’t really make any difference to the species’ prospects long term,” Mr Burton said.

For those of you who enjoy the sight of these butterflies flitting all around, it looks good for their continued survival, he added. “They are doing very well, and will continue to do so long as there is Raw-bones in abundance available to fuel their life cycles. They are abundant out east in Grand Cayman because that’s where most of the remaining natural habitat is, and the Raw-bones is particularly abundant in coastal and interior shrubland.”

So there you are. I hope Mr Burton was able to satisfy your curiosity and calm any fears that you might have about causing any decline to the population of our Great Southern White butterflies.

You can read more about butterflies in the Cayman Islands on the DOE website here.

Tags: Fred Burton, Great Southern White butterfly

Category: Ask Auntie, Conservation Questions