One of the common rainforest trees in the Illawarra is the fig. Actually there are five species here, including the Sandpaper Fig, Port Jackson Fig and Moreton Bay Fig. They belong to the same genus of plants (Ficus) as the domesticated fig from Europe.

All figs share a strange trait – their flowers are inside-out – that fleshy fruit that you eat is really the cup of a flower curved up and around itself, so that the flower parts are on the inside. These are the parts that need to be pollinated to produce seeds.

The dispersal of the seeds is easy – fruit bats and birds eat the figs and then scatter seeds in their droppings. You can see small fig plants growing on (slightly) neglected buildings in Sydney and I like to think that if Sydney was suddenly abandoned it would become like Ankor Wat when discovered by Europeans – huge fig trees growing over and collapsing the buildings underneath. Fun for the Martians to excavate, when they arrive.

But what about the pollination? All figs are pollinated by tiny wasps. It’s an example of a symbiotic (mutual benefit) relationship – the wasp pollinates the flower, some flower parts are sacrificed as wasp food, and both are safely hidden away. The insect life cycle is a bit strange: males are wingless, so can only mate with their probable sisters inside the fig and it’s only the winged females that disperse to pollinate figs – by entering the small hole at the top (the ostiole).

That all sounds very nice and simple – my understanding was one fig species, one wasp species to pollinate it. However, when I cut open a Port Jackson Fig (from Hyde Park in central Sydney) I found three different kinds of wasps. What is going on?

Fortunately there is an expert on figwasps locally, Professor James Cook, University of Western Sydney. James has kindly helped me out here. In the sample photographed there appear to be five different wasps, but male and female pairs of two species look so different. James has identified these as:

• 1. black females with short ‘stings’ (egg-laying organs) and wingless males with dark heads. This species is the main pollinator;
• 2. green female with long ovipositor and wingless males with big pale heads (blue dots). This is a predator of the figwasp.
• 3. very flat wingless males (e.g. seen sideways at right of centre) without females in sample (green dots). These cause swellings inside the fig, where the larvae grow.

So it isn’t a simple system at all, and there is a lot more to this. Some wasps cheat the plant by ovipositing and emerging without contact with pollen. Males, often brothers, may kill each other. Nice.

The great thing is that studying these tiny worlds is easy – maybe a school project?

Further reading:

(1) DeGabriel and others. 2021. Journal of Insect Conservation and Diversity. A study of the diversity of figwasps in the Sydney area.

(2) Everything about figs and figwasps.