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How stag beetle Lucanus cervus larvae pupate

by Paul Hendriks and Maria Fremlin.

This page describes the most secretive period in the life of Lucanus cervus - pupation.
A mature stag beetle Lucanus cervus larva leaves the wood where it fed and at a depth of 30-50 cm builds a cocoon: a safe place where it will change into a pupa and the future beetle may lie for months to come.
Here we describe step-by-step how the metamorphosis from larva to beetle took place by following one single larva in captivity, meticulously. This larva was reared by one of us, Paul Hendriks, at room temperature, from egg to beetle, starting on August 2008, and, at the beginning of April 2010, it was placed in a shallow glass box with an easily opened glass lid. This made it possible to observe and photograph it throughout.

This page is divided in three sections: cocoon making, pupation and eclosion at the end of which there is a summary of the time elapsed and the weight losses incurred.
If you pass the mouse over the photos you will get, when available, information about age, size, weight and the date.

Cocoon making

The larva that you see below is fully grown and ready to make its cocoon.

18 months, L3, hcw=10.5 mm, 13 g. Photo 6 April 2010, Paul Hendriks The white/yellowish tissue of the larva was built up over a long feeding period on decayed wood. You can see the dark contents of its gut showing through its skin.

The larva entered the third larval stage in December 2008 and fed until the beginning of April 2010.
During that period (15 months) the larva's weight increased from 3.5 g to 13 g.

From now on this larva is not going to feed any more.

Photo 22 April 2010, Paul Hendriks
In the picture on the left you can see the larva's work in progress.

The dark coloured parts in the soil, right, are part of the cocoon. It is an oval cell with the smooth walls of very tightly compressed soil.

You can see that the larva is in a cavity, left. It is scraping the soil and transporting it backwards to the cocoon.

Photo 23 April 2010, Paul Hendriks
The following day the larva shut the cocoon and inside continued working on it.

While it was doing so, it continually pressed its head to the walls, thus compressing the soil.

Only the contours of the cocoon can be seen in the picture - the dark coloured soil - and a bit of the larva.

19 months. Photo 29 May 2010, Paul Hendriks
About one month later, the larva fully visible inside its cocoon.
The larva has been working on it for approximately 6 weeks.

Its skin is now wrinkled and less shiny.

These changes in the larva are caused by the emptying of its gut. All its contents will be excreted by the larva.
The larva will spread them on the cocoon walls.

11 g. Photo 5 June 2010, Paul Hendriks
The larva has now emptied its gut completely; it lost 2 g since it started making its cocoon.
Now it looks like a very “old” larva, compared with its first picture. Apart from its very wrinkly skin, the larva has also become considerably smaller and it doesn't move as easy as a larva before pupation.
The emptying of the gut contents took the larva a week or so. Nothing could be seen of this excretion loose inside the cocoon. The larva processed all of it neatly onto the wall which was now very smooth. This very is important because as you are going to see later any debris in the cocoon would cause deformities in the adult.
20 months. Photo 12 June 2010, Paul Hendriks
One can tell that a larva in this resting stage is not far from pupating.

The larva stretches itself in a characteristic way, as can be seen in the picture on the left. It is called a pre-pupa.

During the period that the larva had emptied its gut, hardly visible changes had been taking place inside it. For instance, a new skin was developing under the old wrinkled skin.

Time elapsed since the larva started making the cocoon: 68 days
Weight loss: 2 g

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Pupation normally takes about half an hour to happen. The larva starts to make a pulsating movement from the abdomen to the head.
After a while the hard head capsule bursts and the old wrinkled skin splits open along the back, and, like a sort of jelly, the new form emerges. It moves to and fro, thus shedding the head capsule and the old skin (the exuvia).
After that, the antlers, legs, etc, are stretched.

Photo 13 June 2010, Paul Hendriks
On 13 June, early in the morning, the larva pupated, left.
This pupa is just a few hours old and looks like it is made of jelly. Some parts are nearly translucent, like the antlers.
When you look at the former picture of the larva and compare it with the picture of the pupa, it becomes evident what great changes have taken place.
You can also imagine how fragile such a pupa is. Therefore a good cocoon is very important for its protection.
Photo 15 June 2010, Paul Hendriks
A few days later the pupa got a yellowish/orange colour.
You can see the pupa from the side.
In this position you can see that its antlers and head are folded in front of its “chest”.

In its cell the pupa wriggles with its abdomen from time to time and is thus able to turn over. This way it prevents lying in the same position too long.
And this is just what a bedridden person should do to avoid bed sores.

Photo 23 June 2010, Paul Hendriks
Eight days later the pupa still looked about the same. Now you can see it on its back.

Its wings and wing cases are not on its back yet, but neatly folded over the chest as you can see in the former picture.

Pupation has caused further weight loss as well. Part of that is because of the loss of body fluids as well as the shed skin.
You can see it lying at the right side of the cocoon in this picture as well.

9 g, 5.5 cm. Photo 9 July 2010, Paul Hendriks
In this picture you can get an idea of the size of the pupa.

You can also see that the antlers are a bit more orange than the rest of the pupa.

It weighed 9 g.

Photo 17 July 2010, Paul Hendriks
It is now 17 July and the pupal stage is slowly coming to an end.
This you can see by the colouration of certain body parts under the skin.
If you look closely, you can see that the head, antlers and legs shine through the pupal skin.
The wings and wing cases will get their shape and colour after the beetle emerges.

Duration of the pupation stage: 36 days
Weight loss: 2 g
Total time elapsed since the larva started making the cocoon: 104 days
Total weight loss since start: 4 g

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With movements of its legs and head the beetle opens the pupal skin. Below you can still see this skin on its head.
An important change is that the wings and wing cases are now folded on the back and are getting their final shape.

Photo 19 July 2010, Paul Hendriks
On 19 July, in the morning, the beetle emerged, and it has successfully turned over. This is very important because its wings are very soft and wet.

As you can see the soft wings are still sticking out of the wing cases to dry out. Later on the beetle folds them under.

If you see a beetle with a deformity on the wing cases, it is often caused during this stage. If there were any irregularities in the cocoon, the still soft wing cases would take the shape of these irregularities when the beetle is lying on them.

Photo 18 July 2010, Paul Hendriks
Here you can see the beetle some minutes later. It got rid of the pupal skin on the head.

Note how it fits perfectly in its cocoon!

So far 36 days have elapsed and the metamorphosis into a beetle is nearly finished; several parts of the beetle, like the wing cases, still have to dry and harden.

Photo 21 July 2010, Paul Hendriks
In the photo on the left, the beetle still has brown/purple parts at several places on its body. These parts will become black or brown in due time.

The wing cases have hardened and coloured almost fully and the soft wings are folded under the wing cases.

6g, 7 cm. Photo 22 July 2010, Paul Hendriks
Apart from the hardening of some parts of the beetle, the emergence is now complete.

It all started indoors early April with the larva that commenced working on its cocoon until the final hardening of the beetle towards the end of July.

These wondrous transformations took place in about 15 weeks. At the end the beetle measured 7 cm and weighed 6 g, less than half the weight of the larva before it started building its cocoon.

Duration of the hardening of the eclosed beetle: about 7 days
Weight loss during eclosion: 3 g
Total time elapsed since the larva started making the cocoon: 111 days
Total weight loss: 7 g

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Now a long period of rest and waiting starts; if it were in the wild, the following spring, sometime at the end of May or the beginning of June, the beetle would emerge to reproduce itself. And at about the same time mature Lucanus cervus larvae will be making their preparations to pupate, for more see Pupal stage in the wild.

Paul has written about this in Dutch, see:
Hendriks, P. (2011). De ondergrondse metamorfose van het Vliegend hert. De Levende Natuur 112 (1): 27-28. [PDF]

If you found this page interesting then we would love to get some feedback from you. Just contact Maria Fremlin!

Last modified: Thu Jun 21 16:43:36 BST 2012

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