Gardd Fotaneg Genedlaethol CymruNational Botanic Garden of WalesNational Botanic Garden of Wales
Garden blogs

Plas Pilipala: the swallowtails

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Since the swallowtails have started laying eggs on the Citrus in Plas Pilipala, we’re now on to about our ninth plant, which shouldn’t be too surprising. In the same way the cabbage white can go through a veg patch, certain Papilio species are known as pests of citrus plantations. We don’t mind though, especially when you can get to see these beautiful jewel-green caterpillars.

The main swallowtail we have laying is the Common Mormon swallowtail, Papilio polytes. The males of this species all look the same; plain black with a cream stripe. The females can look like the males, but they also show more impressive forms; ones with a lacy trim and red patches. These female morphs are actually mimicking the appearance of a different swallowtail species; one that’s toxic and inedible. 

The other thing we quickly learnt about our caterpillars is that they look completely different when they first hatch compared to when they’re ready to pupate. When they first appear, as dust-speck sized creatures, they are dark grey with mottled white stripes (distinctly bird dropping-like). They stay like this as they get bigger and bigger until, once they’re about the size of a thumbnail, they transform into their green-banded appearance that blends in with the (remaining) leaf color.

It’s one thing to see all of the chrysalises lined up neatly in our emergence cage, but once you spot a pupa clinging to a stem or under a leaf, you can really appreciate the principle of the camouflage. The Common Mormon chrysalises are well hidden, with a single thread silk harness securing their middle to the stem.