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Stag beetle larvae found in woodchip beds

It is known that stag beetle larvae can be found in the vicinity of sawmills, feeding on the rotting wood waste piles. Shown below, side-by-side, are a couple of unusual experiences, in very different locations, where the stag beetles took to breeding in woodchip beds. Hopefully the analysis of their history will enable us to understand why stag beetle larvae were found thriving in both sites.
 
 
 London, England
 


 Veluwe, Netherlands
 

Where Path being built. Photo by Pat Robison, 25 February 2005.
 
Winding foot path built in a small nature reserve. Final length 135 m long, 1 m wide, facing south in the photo, courtesy of Pat Robinson.
This photo shows the path after the woodchips were dug out in preparation for the hoggin [1] being laid. For more details see below.
Primary school playground lined with woodchips. Photo by Bert van Geel, July 2004.
 
Primary school playgrounds, total area about 325 m2, facing south. The photo, taken by Bert van Geel, shows the larger one, 225 m2.
Stag beetle area in...
 
A typical London park, of around 4 hectares, with trees around the edge, and enclosed on 3 sides by housing and some commercial buildings. It was probably an ancient field which in Victorian times might have been filled with rubble before conversion into a park. For more details see below.
A village, about 50 to 100 m above sea level, in the vicinity of old forest relics.
Soil
 
As you can see in the photo it is dark due to the rotten woodchips. Elsewhere it is much lighter, more like gravelly clay, therefore more free draining than the area surrounding the park, which is on very heavy clay. Well drained sandy soil.
Weather Average annual rainfall around 630 mm/ 25 inches.
Average annual rainfall around 800 mm.
Lowest recorded winter temperature: -20o C.
Built
 
1999 and extended by 15 m one year later. 1980
How it was built The path was built through an area that had been planted in 1997 with trees, which were then heavily mulched with aged woodchips from a site in the west of the borough (they can be seen in the top photo).
However while the path was being dug quite a lot of household rubble was found plus some stag beetle larvae as well, the latter were relocated nearby. It was excavated to a depth of 15-20 cm, unlined, then filled with fresh hardwood chips.
The school playgrounds were dug to a depth of 30 cm, lined with a Nicolon membrane, then filled with fresh hardwood chips.
Hardwood chips From London hardwood street trees, mostly London plane Platanus x acerifolia and lime Tilia spp.. They were provided free of charge from the London Borough Tree Service. Usually from a site nearby to save transport costs, and if so freshly cut. From the village hardwood trees, freshly cut. The trees are: beech Fagus spp., ash Fraxinus spp., oak Quercus spp., and probably also poplar Populus spp., willow Salix spp., etc.
Maintenance Topped up with fresh woodchips as necessary, roughly two or three times per year. Topped up with fresh woodchips every five years. Luckily they don't remove the old ones.
Findings Some of the stag beetle larvae, Photo by Pat Robinson, 27 February 2005.
 
When the path was extended some larvae and adult stag beetles were found, which were relocated.
In early 2005 the woodchips had to be removed in order to make a more durable path, for which money had become available. See top photo.
In the process over 750 stag beetle larvae, a few live stag beetle imagos, and some sawfly larvae. See a sample above. Photo courtesy of Pat Robinson.[2]
All the larvae were relocated to an area of woodchip and logs within the nature reserve, see photo below.
One rhinoceros beetle larva, middle, and two stag beetle larvae. Photo by Bert van Geel, 27 July 2004.
 
In July 2004 9 large stag beetle larvae, 200 rhinoceros beetle larvae, and one dead male stag beetle imago, were found in a short time just round the edges of one playground.
The photo, taken by Bert van Geel, shows, two stag beetle larvae and one rhinoceros beetle larva in the middle. [3]

Subsequent monitoring of these woodchip beds:
In 2006 only rhinoceros beetle larvae were found, no stag beetle larvae at all (John T. Smit, pers. com).
In September 2007, 263 rhinoceros beetle larvae and one L3 stag beetle larva were found by Paul Hendriks and Maria Fremlin.

Conclusions Within six years of being built in a stag beetle area this woodchip path became a fantastic stag beetle nesting area.
People walked on the path regularly without apparent damage to the larvae. The larvae could easily pupate in the soil at the level of their choice.
Stag beetles were spotted in the area during the summer 2005.
The stag beetle larvae were found, quite by chance, while searching for rhinoceros beetle larvae.
Children trampled on the woodchips regularly and it seems to have made no difference.
Stag beetle and rhinoceros larvae seem to be resilient, and adaptable. They have had to pupate above the membrane, and seem to have survived the cold winters.
Future London woodchip pile. Photo by Pat Robinson, 16 April 2005.
 
Experimental artificial stag beetle habitat created with a high ratio woodchips-to-logs.
London woodchip pile. Photo by Pat Robinson, 16 April 2005.
 
Another experimental habitat, this one with an even higher ratio woodchips-to-logs. Photos courtesy of Pat Robinson.
Subsequent monitoring of these woodchip beds:
In July 17 2008 one L3 stag beetle (Lucanus cervus) larva, and several imago lesser stag beetles (Dorcus parallelipipedus) were found by Maria Fremlin.
Woodchip beds from hardwoods seem to have been very successful in these two locations, both in known stag beetle areas; they provided a good nesting habitat not only for stag beetles but for other saproxylic invertebrates as well. Why?
Possibly the main reasons were (i) they rot very quickly, and (ii) they act as a very good mulch, thus conserving the moisture, both being very important factors for a successful nesting habitat.
Because of these experiences, in very different situations but yet so similar, there is probably great future in the role of woodchips for maintaining, and possibly increasing the population, and very gradually restoring the range of stag beetles. [4]
Therefore future artificial nests could be built, in known stag beetle areas, with these findings in mind. All that needs to be done is to considerably increase the ratio woodchips-to-logs, see left photo.
Maintenance is very important, all artificial nesting habitats benefit from being topped up regularly with woodchips. It is sometimes very difficult to strike a good balance with artificial habitats; for instance, note that on the photos above there are logs lying on the surface, not buried. Logs like that could easily dry up if not topped up. In the original pyramid design the logs are buried to a good 50 cm, at least, so that down below they do stay moist. That way perhaps there is not such a strong need for mulching with woodchips. [4]
However, if artificial nests are built outside stag beetle areas, then the results might be quite different; stag beetles are a “stay-at-home” kind of beetle. [4]

[1] - Hoggin is the term given to a mixture of clays, sands and gravels to form a material that compacts well and provides a usable, stable surface at low cost.
[2] - Some sawflies (Hymenoptera: Symphita) can live in decaying wood during the larval stage. See The invertebrates of living & decaying timber in Britain and Ireland - A provisional annotated checklist. No. 467 - English Nature Research Reports. Compiled by Keith N A Alexander, 2002. [PDF, 2.6 MB].
[3] - The rhinoceros beetle Oryctes nasicornis (Coleoptera: Scarabaeidae) is not known to occur in the British Isles, but is very common in the continent. Their larvae feed on decaying wood, thus sometimes they are found sharing the habitat with the larvae of stag and lesser stag beetle in people's gardens.
[4] - Behoud van het Vliegend hert (Maintenance of stag beetle habitats), by Hendriks, P. and E. van der Ploeg (May 2006). Vakblad Natuur Bos Landschap, 9-12.

LINKS:
Woodchip fungi - A very interesting site about the “woodchip community”, by Peter Shaw.
Broedstoven voor vliegende herten - Breeding sites for stag beetles, by John T. Smit & Paul Hendriks, 2005.
Vliegend hert - Stag beetle, by Smit, J.T. 2004.
Larven in soorten en maten, by Smit, J.T. 2005 - A very interesting article comparing stag beetle larvae with the rhinoceros and cockchafer larvae.
Veluwefotografie vliegendhert - Gerrit Rekers photos of Veluwe stag beetles in their natural habitat.
Fotogalerij Jan Henderickx - Rhinoceros beetle Oryctes nasicornis (Coleoptera: Scarabaeidae) photos by Jan Henderickx, a comprehensive collection which includes their habitat.
Videos of feeding stag beetle (Lucanus cervus) and rhino beetle (Oryctes nasicornis) larvae by Paul Hendriks in YouTube.

Acknowledgments

Contact: Maria Fremlin
Last modified: Sat Feb 12 10:32:23 GMT 2011

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