Tuesday, May 13, 2014

Ants in your plants--symbiosis in the Wet Tropics

Prickly Ant Plant at Keating Lagoon near Cooktown
Ants in Your Plants! Not in your pants. That's a children's ditty.

Prickly Ant Plants.
Symbiotic or mutual relationships in nature can be very fascinating, but here's one that beats them all.

It's a triple whammy of the natural world and it taking place right now throughout Cape York.
You can find specimens in the  among the mangroves at Cowie Beach, along Marrja Boardwalk at Cape Tribulation, among the melaleaucas at Keating Lagoon outside Cooktown, and the Natures Powerhouse Botanic Gardens at Cooktown.
 By far the most easily spotted is in the gardens outside James Cook Museum, where one endemic  Ant Plant species is nicely plaqued and presented on a paperbark tree.

Ant plant at Marrdja Boardwalk growing among mangroves

The Ant Plant (myrmecodia beccarii) is an epiphytic plant with fibrous inner chambers. It usually grows on paperbarks (melaleucas) or mangrove species. Superficially, it looks like an orchid, but close up, you can see that the outside is covered with prickles.
The real action is inside. Golden ants live inside the chambers and patrol the plant to remove leaf-eating pests. Their excreta is absorbed as food by the plant. That's a genuine symbiotic or mutual relationship.

The next symbiotic layer is the arrival of the Apollo jewel butterfly, the larvae of which live inside the plant. They seem to eat either the ant plant tissue and leaves or ant larvae. The butterfly larvae then provide honeydew as food for the ants. In appreciation, the ants protect the larvae.

Complicated? Incredibly so! Interdependency or mutualism--sometimes co-operative, sometimes not.
Figs need wasps to pollinate each and every fig. Buff-breasted paradise kingfishers bore a hole into and inhabit termites nests.

Peppermint spray in the Wet Tropics rainforest

Rainforest spray

What’s  a quirky blueish-green colour and spits out peppermint spray?

It’s not a seasick sailor, but a very unusual insect, called the peppermint stick insect (or megacrania batesii).
A coupling pair of peppermint stick insects

There’s no other  insect –or insect colour for that matter-- quite like it. We only get them in the Wet Tropics World Heritage rainforest, mainly in the northern end, around the Cow Bay to Cape Tribulation areas.

They don’t really spit, rather they squirt from their backs. When disturbed by a predator, they send out a surprising sweet-smelling spray of milky-white gooey peppermint. Just enough to sting the eyes of a preying spider or bird, or surprise a curious tourist.

Their diet is the serrated leaf of only the pandanus plant (aka scrub breadfruit), in which they also hide skilfully.   While indigestible food to us, it's the bread of life for peppermint stick insects. 
Even when they are inextricably entwined, like the coupling two in the accompanying photo, they are almost perfectly camouflaged among the pandanus leaves. The male is the much smaller of the two, but with better wings, does most of the flitting around. She is bigger, and can fly but doesn’t much need to. She just drops the fertilised eggs down the leaf, where they hatch a few months later.

When I think insects, I think of the Daintree Entological Museum (the Insect Museum) near Cooper Creek. Apart from its collection under glass, you usually see spiny leaf insects, Goliath Stick Insects and, if you’re lucky, a caterpillar of the Giant Hercules Moth. It’s off Turpentine Road, twenty minutes drive south of Cape Tribulation, or 70 minutes north of Port Douglas.

Where to find the little fellas

Where else can you find the Peppermint Stick Insect?
Their Pandanus food lives mainly in swampy areas and near the beach, so that’s where you’ll most likely find them. Try alongside Thornton Beach, Kulki (around the Cape Tribulation Carpark and toilet area), Dubuji Boardwalk and in Myall Beach area around  the Cape Trib Campground. They are all good spots. Look for the telltale signs that the pandanus leaves have been freshly eaten.

Tasting Notes

 Only peppermint Stick Insects would eat pandanus leaves—have you ever tried them? Don’t. They’re too prickly for a start.