At first you think that orchids are about beauty, serenity, fragility and the surprising brilliance of their blooms.
Then you hear about a sexually deceptive orchid with a small potato-like growth that is in cahoots with a parasitic wasp that lays its eggs in beetle larvae (the wasp larvae eat their way out from the inside).
It’s a process known as pseudo-copulation. The wasp it tricked into thinking that the flower is a female wasp.
The yellow-lip spider-orchid (Caladenia xanthochila) is listed as endangered in Victoria. In the Loddon Mallee region there a just three of the plants.
Two of the three specimens that are known in the area are in Kooyoora State Park, and the reintroduction of 100 new plants this year has conservationists abuzz.
‘This has been a long time coming,’ says Julie Whitfield, the leader of the Loddon Mallee Orchid Conservation Project. She’s right—they’ve been attempting to propagate yellow-lip spider-orchids at the Royal Botanic Gardens in Melbourne for nearly a decade.
The yellow-lip spider-orchid is so intricately interlinked with its habitat and the species that surround it that reproducing the right conditions for growth proved extremely difficult in a lab setting.
At first, the plant seems drab. Each individual has one leaf: green with a purple base and hairy. But it doesn’t have it all the time—the yellow-lip spider-orchid is a deciduous plant. They are also tuberous—they have a skinny potato-like growth that sits under the ground and stores nutrients.
The orchid relies on microscopic fungi around the tuber to feed it nutrients.
In fact, if the fungi isn’t right there ready to provide the right nutrients, seeds will not germinate. Yellow-lip spider-orchid seeds do not have endosperms—the nutrient packages that allow plants to sprout on their own.
When the orchid matures and the conditions are perfect, it puts up a flower in order to attempt to reproduce.
A tiny stalk slivers up out of the ground, becomes quite sturdy, and a pale greenish-yellow flower unfurls. The thin petals splay out like a starfish, with a meaty section in the centre that looks a little bit like a mouth with a tongue sticking right.
It gives off a smell, but not a sweet scent to attract honey eaters. Rather, it gives off a pheromone that smells like a female thynnid wasp.
‘The female wasp is a tiny little ant of a thing. She’s very, very small and she can’t fly,’ says Julie Whitfield.
Ironically, she feeds on nectar-producing flowers, which are often high up on the top of shrubs or trees.
‘So she climbs herself to the top of a grass or a shrub, or something along those lines, and will actually give off the pheromone that will attract the male wasp in to collect her up and mate with her,’ says Whitfield.
‘While he’s mating with her in flight, he will “take her out for dinner” in a sense, and will take her up to the canopy to feed on the eucalypt flowers or the hakea flower or whatever is around. And then once he’s finished mating with her he will put her back down on the ground so she can go about her business.’
The yellow-lip spider-orchid takes advantage of this mating behaviour by pretending to be a female wasp.
‘It’s a process known as pseudo-copulation,’ says Whitfield. ‘The wasp it tricked into thinking that the flower is a female wasp.
‘Not only is the flower itself giving off a pheromone, there is a labellum, which is supposed to—I wouldn’t exactly know because I’m not a wasp—feel like a female wasp as well.
‘So it’s the right shape and smells the same, so when the male flies in and tries to attach itself to the labellum and pick it up and fly away with it, it’s tricked into cross-pollinating these plants.’
The male wasp will try and try again with the orchid, especially if there are no active females in the area, and can be observed getting more agitated by the experience.
There is no positive feedback for the male wasp— he gets no nectar and he gets no female. The orchid, on the other hand, gets pollinated.
‘[The relationship] is so specific that even within the same genus there are specific species [of wasps] that are responsible for pollinating specific species of Caladenia,’ says Whitfield.
‘Then the story goes even deeper than that. The wasp for these Caladenias is actually a parasitic wasp, so it also parasitises scarab beetle larvae.’
Scarab beetles have larvae that are sometimes called ‘curl grubs’. They’re big thick, milky-white grubs with dark heads that live underground.
The female wasp will dig down into the soil and lay her eggs directly into the grub. When they hatch and grow, they emerge right out of the grub’s body.
‘These relationships signify it is how important it is to maintain our ecosystems as a whole,’ says Whitfield.
‘It needs to be understood that within and ecosystem there is nothing that is insignificant, there is nothing that is more important or less important than the next thing.
‘These things all work together and there are relationships going on out there that we don’t know about, that we couldn’t possibly understand.’
Without these helpers in their ecosystem the orchids would experience a genetic bottleneck and would slowly die out. And each of the Caladenia species in the Loddon Mallee Project has its own very particular set of requirements.
If one link is missing in the chain, there will be no orchids.
Threats listed for the yellow-lip spider-orchid include development, fire, grazing, drought, illegal collection and pesticide runoff.
The situation is dire.
‘We won’t have some of these species by the time I have grandchildren,’ says Whitfield.
Julie Whitfield is from Amaryllis Environmental, and is administering the Loddon Mallee Orchid Conservation Project on behalf the Victorian Department of Environment, Land, Water and Power, funded through the Victorian Environmental Partnerships.
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