Giving as good as you get: the eyed hawkmoth’s fight to survive

The eyed hawkmoth is on first glance an unassuming moth, in spite of its large wingspan. This seemingly demure character, however, has a little hidden secret: it’s really rather feisty. Should you provoke it, this moth will flash its hindwings in frustration, revealing a tantalising glimpse of its cold blue ‘eyes’.

Adult eyed hawkmoth
Adult eyed hawkmoth

As BBC Wildlife reported in June, scientists have now confirmed the long-held common sense belief that eyespots are intended to imitate eyes, therefore allowing the butterfly or moth to appear to be much larger and more threatening than they really are. However, this is not the only trick in the eyed hawkmoth’s armoury. Their body will pulse softly up and down as they display their eyespots, intimidating their potential predator with their supposed size and their fearless exhibition.

In preparation for one of our beginners’ ‘taster sessions’ on moths at Brandon Marsh Nature Centre, a moth trap was set the night before to ensure that there were a few moths to show the participants of the session. A female eyed hawkmoth was caught in that trap. All the moths were carefully and individually stowed in plastic boxes and put in a fridge. The temperature of a fridge is cool enough to encourage the moths to stay still rather than attempting to fly (as they would on a warm summer’s evening), therefore they become calm. Yet when the eyed hawkmoth was retrieved from the fridge later that morning, a discovery was made. She had begun to lay eggs.

Eyed hawkmoth caterpillars at 1 week old
Eyed hawkmoth caterpillars at 1 week old
Eyed hawkmoth caterpillars at 1 week old
Eyed hawkmoth caterpillars at 1 week old

In a working environment filled with keen conservationists there was only really one course of action to take. In a similar fashion to 2014’s puss moths, the staff at Warwickshire Wildlife Trust decided to rear the caterpillars and capture their journey to pupation.

Eyed hawkmoth caterpillar - 6 weeks old
Eyed hawkmoth caterpillar – 6 weeks old
Eyed hawkmoth caterpillar - 6 weeks old
Eyed hawkmoth caterpillar – 6 weeks old

Caterpillars are no less at risk than their adult counterparts in the cutthroat world of your garden, local parks and nature reserves. So the scrappy nature of the adult eyed hawkmoth is just as present in its former incarnation as a caterpillar. In attempting to transfer them from stems of old food to freshly picked sallow (a type of willow) or apple, the rearer gets a unique insight into their incredible ability to resist being picked up by predators. They seem to stick to the stem, wriggling in agitation, and flatly refusing to let go. By the time they are 6 weeks old, and very nearly the width of a human palm, there is quite simply no lifting them (unless perhaps, like a hungry bird, you are also determined to eat them).

As the caterpillars reach the size at which they can pupate, they begin to change colour, turning a darker green (see the left-hand caterpillar in the image above) and gradually acquiring a purple hue. The eyed hawkmoth caterpillar then does something rather unexpected: dropping from the tree, the caterpillar buries itself in the soil and from there it will pupate.

Beginning to pupate - the dark-coloured caterpillars have formed the pupa; the green ones are yet to shed their outer layer of skin
Beginning to pupate – the dark-coloured caterpillars have formed the pupa; the green ones are yet to shed their outer layer of skin

The caterpillars once they have all pupated. In these images they have been dug up from where they had buried themselves in the soil in order to demonstrate the process
The caterpillars once they have all pupated. In these images they have been dug up from where they had buried themselves in the soil in order to demonstrate the process
The shed skin of a caterpillar
The shed skin of a caterpillar

Within the pupa, the caterpillars effect one of nature’s greatest transformations. The pupa itself retains the small holes down its sides that the original caterpillar used to breathe. With access to oxygen through these holes the cells in the ‘caterpillar soup’ can gradually form into the adult moths. These will emerge in May 2016, be on the wing between May and July, perhaps lay their own strong and scrappy eggs, and flash their eyespots angrily at anything that dares to attempt to eat them.

Emma

Images: adult eyed hawkmoth copyright Simon Thompson (WWT) 2015; all caterpillar images copyright Emma Richmond (WWT) 2015.

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