Illustrated stag beetle Lucanus cervus life cycle

Stag beetles have a very secluded long life cycle, spent mostly underground, and this page is an attempt to illustrate it step-by-step. Understandably there are still a few gaps to cover, so contributions are always very welcome.

Breeding season: from the end of May until the beginning of August out in the open air. As soon as the beetles emerge all they want to do is to mate.

Stag beetles clinging to ivy in the mating position. Photo by John Allen.

Stag beetles mating during the evening under a car. Photo by Maria Fremlin, 7 June 2003.

Stag beetles mating during the night. Photo by Maria Fremlin, 17 June 2006.

Male stag beetle attempting to mate with a dead female. For another photo click here. Photo by Maria Fremlin, 6 July 2007.

It is not that easy to find stag beetles mating, these photos are the result of very lucky encounters!
For more about their mating behaviour in the wild, click here.

Eggs: nobody knows for sure how many but in captivity they may lay around 30 eggs, in some cases up to 90 * . The eggs are laid singly next to rotting wood and before she lays them she may take a long time carefully preparing her nursery, digging around, chewing pieces of wood, and compacting them near the dead wood. As each egg is laid she uses her retractable ovipositor to form a hollow around it, and in the process might be passing on some important microorganisms essential to their larvae development [1].
Females probably do not lay all their eggs in one “basket”, sometimes they might go from stump to stump and possibly this is what they are doing when one sees them walking about late into the season [2&3].

Eggs from a female that had been trodden on. They are oval shape and surrounded by fat. Photo by Maria Fremlin.

Fertilised eggs take up moisture and change shape as the larvae grow inside. Photo by Maria Fremlin, 2 August 2009.

View of an egg showing the larva developing inside it; it is now 3 by 3.4 mm. In order to come out the larva will cut the shell with its sharp pincers. Photo by Dr Eva Sprecher.

Egg and freshly hatched larva. Photo by Maria Fremlin, 2 August 2009.

The eggs take about 3 weeks to hatch.

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Larval stage: again, nobody knows for sure how long it takes in nature. However, recently, it has been observed that the larval stage took less than 4 years when feeding on decaying oak posts in the wild [4].

First instar: age - two days weight - 0.02 g HCW - 2.4 mm length - 5 mm Photo by Dr Eva Sprecher.

Second instar: age - twenty two days weight - unknown HCW - ~5 mm length - ~4.5 cm Photo by Paul Hendriks.

Third instar: age - ~4 months weight - 3.3 g HCW - 10 mm length - unknown Photo by M. Fremlin.

Third instar: age - unknown weight - 21.5 g HCW - 11.95 mm length - 8 cm Photo by Bert van Geel.

It might take quite at few years feeding on decaying dead wood to grow from a tiny fragile grub (left) to the unusually enormous fat larva shown on a man's hand (right). To start with stag beetle larvae grow quite quickly, however they will stay a long time fattening up in the last instar. The thin 3.3 g third instar larva was found under an old oak log that had been moved into that position the previous year.
In the same nest one can find larvae at different stages of development, as Heinz Rothacher has.
Interestingly, from some captivity studies, it was found that the tiny larvae might undergo more than the well known three instars before they are ready to pupate [5].
If you want to know more about stag beetle larvae click here.

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Pupation stage: between three and six weeks during the summer inside a cocoon, in the soil, made of compacted soil.
In the wild prepupation gets well under way before the end of July in the UK; further south it occurs later [2].
When they are fully grown the larvae stop eating and leave for the soil where they will make a cocoon and inside it the larvae will undergo metamorphosis in a protected environment.

Larva ready to pupate, it has changed shape and colour. Photo by Maria Fremlin, 3 August 2008.

More changes have occurred, it now looks a bit like a doll; pupa in Latin means a doll. Photo by Maria Fremlin, 14 August 2008.

The larva has now metamorphosed into a pupa and shed its skin which has split right down the back. Photo by Maria Fremlin, 15 August 2008.

At this stage the larvae have gone through metamorphosis and now the pupae bear a very close resemblance with the adult beetles. Note below how easy they are to sex.

Male stag beetle pupa. Photo by Michele Zilioli, September 2005, Italy. The larva was collected in the wild feeding on a rotting oak stump, Quercus petra, and then reared in captivity.	Female stag beetle pupa. Photo by Paul Hendriks, November 2007, The Netherlands. Reared in captivity from eggs laid in July 2006.	The pupa on the left has now metamorphosed into an adult stag beetle female; its wing cases are not quite dark yet. Photo by Paul Hendriks, November 2007, The Netherlands.

The cocoon is nice and smooth inside. It is held together by special larval secretions and lined with the gut contents, it provides essential shelter for the very vulnerable pupa.

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Adult stage: the imago may stay inside the cocoon or not. In any case it will always remain under the ground for several months until it emerges at the end of the spring. It emerges around late May in the north [5] but a bit earlier in the South [2], then it flies outside.

Male stag beetle, apparently still inside its cocoon, found in Richmond Park, London, on 26 January 2007 when a dead tree fell down. Its antlers were spotted in the soil that was still attached to the tree; it was probably 30 cm below the ground before it was disturbed. Photo by Mark Wagstaff.

Male stag beetle found inside its cocoon, late May. It was at 40 cm depth, near the rotten roots of an ash (Fraxinus spp.) tree where stag beetle larvae were also found feeding. Click on the picture for another view. Photo courtesy of Heinz Rothacher.

Female stag beetle found inside its cocoon, early April, 2006. It was in the roots of an old oak (Quercus robur) stump, about 3 meters high. There was also 1 larva, 7 females, of which one was dead, and 14 males, of which 4 were dead. Photo by John T. Smit.

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Emergence:

Stag beetles will make their way up to the surface and emerge through holes like this one. They do it with the help of their mandibles and their front legs which are also very strong. Photo by Maria Fremlin, late May.

This beetle was right underneath a fresh hole; it nearly bit an enquiring finger. For more about this nest click here. Photo by Maria Fremlin, 16 May 2009.

Male stag beetle emerging between the slabs of the pavement along a London road in the vicinity of Richmond Park. This photo appeared in the Richmond Park Biodiversity Action Plan, page 96. Photo by Mark Wagstaff, 26 May 2005.

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* http://www.insect.jp/document/rep05/rep05.htm - In this website a Japanese breeder managed to get 90 larvae from one female stag beetle, in Japanese.

References:
[1] - Tanahashi, M., Kubota, K., Matsushita, N.& Togashi, K. (2010) - Discovery of mycangia and the associated xylose-fermenting yeasts in stag beetles (Coleoptera: Lucanidae). Naturwissenschaften 97: 311-317.
[2] - Franciscolo, M.E. (1997)- Coleoptera, Lucanidae, Fauna d'Italia, 35: 228 pp. Edizioni Calderini, Bologna, ISBN 88-8219-017-X.
[3] Kretshmer, K. (2007) - Untersuchungen zum Ausbreitungsverhalten des Hirschkäfers (Lucanus cervus) mittels Radio-Telemetrie Sachbericht. AZ: 51.2.6.02.25-3008/03; Biologische Station im Kreis Wesel. http://www.bskw.de
[4] Smit, J. T. & Hendriks, P. (2005) - Broedstoven voor vliegende herten. Natura, 2: 44-46. [PDF]
[5] Harvey, D. & Gange, A. (2003) - The Private Life of the Stag Beetle ( Lucanus cervus). The Bulletin of the Amateur Entomologists' Society, Volume 62, Number 451, 240 - 244.

Links:
Female Reproductive System - Tutorial by Dr. John R. Meyer, NC State University.
In the female stag beetle there are 6 to 12 ovarioles for each layer in their ovaries. Ref: Scholtz, C.H. and Grebennikov, V.V. 2005: 12. Scrabaeiformia Crowson, 1960, pp. 345-365. Handbook of Zoology, Vol. IV, Arthropoda, Part II, Insecta (edited by N.P. Kristensen and R.G. Beutel), Coleoptera, Vol. 1: Morphology and Systematics (Archostemata, Adephaga, Myxophaga, Polyphaga partim) (edited by R.G. Beutel and R.A.B. Leschen). Walter De Gruyter, Berlin.
Life cycle photos of Lucanus capreolus, a north American species.
Insect life cycles - Interesting life cycle diagrams, by David Kendall.

Last modified: Sat Mar 6 18:01:54 GMT 2010

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