Monarch butterfly and Leichhardt tree

Monarch butterfly
Monarch on Leichhardt tree flower – photo: Liz Downes

A friend sent me this photo and the subject has enough points of interest that I asked her permission to publish it here. The (really obvious) questions are mine, of course – the Q&A format is just for fun.

What is that spiky ball? It’s a flower – more accurately, a flower cluster – of the Leichhardt Tree, Nauclea orientalis.

So the butterfly is sipping nectar from it? Yes. Butterflies are not fussy eaters. They think nectar is nectar, and so long as they can reach it with their proboscises they will take advantage of it.

I’ve seen the butterfly before but not that weird flower. I guess the tree is an exotic? Wrong way round, actually: the tree is a native but the butterfly is a foreigner. It is well naturalised by now but is an American species, the Monarch or Wanderer, Danaus plexippus. Back home, they are famous for their mass migrations. Here, they have spread from Sydney (1871) to Southern West Australia and (obviously) North Queensland.

Is there any connection between the butterfly and the flower, then? Yes, but it’s indirect. The Monarch is a Milkweed butterfly (Danainae, a sub-family of Nymphalidae) and their caterpillars do require particular plants.

Let me guess: milkweeds? Yes – well done! And the botanical family is noted for milky white sap, often poisonous. The caterpillars tolerate and absorb toxins from the food plant, making them distasteful to predators. Local plants in the family include oleanders, frangipani and lots of the smaller weedy plants which grow along river banks.

And the tree? It’s not a milkweed, but it likes wet feet so it grows along river banks too. This one was beside Ross River near the Bush Garden.

And that completes the reasoning: the adult butterfly was near the river to lay eggs on the milkweeds; the tree was near the river for the water; and its flower was a convenient snack for the butterfly.

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