What Big Eyes You Have

An encounter with a grumpy mantis

Bronwen Scott

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Close up of bright green praying mantis against a pale background.
Close up of Giant Rainforest Mantis showing raptorial front legs and surprisingly winsome expression. © Bronwen Scott.

This leaf-green lovely is a Giant Rainforest Mantis (Hierodula majuscula). Just a young ‘un — a nymph* — only 75 mm (3 in) long. When fully grown, this species is up to 110 mm (4.3 in). It is the largest mantis in Australia and one of the largest in the world.

Praying mantis facing to the right, looking at the camera with abdomen raised. The backdrop is dark blue.
What are you lookin’ at? © Bronwen Scott.

Usually found in rainforest in tropical NE Queensland, this one has made itself at home on the potted plants in my collection. (They’re mostly rainforest plants, so fair enough.) It objected to having a camera pointed at it, but elected to move away rather than threaten me and/or the lens. These big insects can display quite an attitude.

Mantis in vertical pose, looking over what I suppose passes for a shoulder against a backdrop of leaves and dark blue.
Draw me like one of your mante religieuse. © Bronwen Scott.

As with other insects, their two compound eyes are made up of thousands of visual structures called ommatidia. Each ommatidium has a cornea and a pseudocone that focuses light on multiple photoreceptor cells. What the mantis sees is a composite image of its surroundings — a 240⁰ view with a 35⁰ overlap at the front. No wonder they are so good at catching other insects. (In the case of the Giant Rainforest Mantis, also lizards and spiders.)

The darker spot on each eye is a pseudopupil, the cluster of ommatidia on the same axis as your line of sight. As the mantis moves its head, the pseudopupil shifts. It results from light falling on reflective and absorbent surfaces — physics! — but it gives the mantis a look that is curious, contemplative or creepy, depending on the your interpretation. This one, I think, was simply cross.

View of a praying mantis from behind/above showing the large eyes and the dark spot of the pseudopupil in each.
Eyes in the back of your head. The pseudopupils and the neat wrap-around view of the mantis. © Bronwen Scott.

Praying mantises have limited colour vision, seeing best in the near ultra-violet and to lesser extent green sections of the spectrum. They are hopeless with orange and red. Even the most adept insect hunters have a weak spot. It seems that other insects exploit it — from a safe distance.

*Mantises, like grasshoppers and cockroaches, do not go through a dramatic metamorphosis as part of development. With each successive moult, they gradually adopt the adult form. The wings in this individual are still small. You can see adult Giant Rainforest Mantises at iNaturalist. This type of development is called hemimetaboly or incomplete metamorphosis.

View of mantis from its left side. It is leaning back, showing the sping forelegs and tiny pale wings which are yet to develop.
Side view showing small wings of the mantis nymph. © Bronwen Scott.

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Bronwen Scott

Zoologist, writer, artist, museum fan, enjoying life in the tropical rainforest of Far North Queensland. She/her. Website: bronwenscott.com