Swedish Institute of Space Physics, IRF
The evolution and the life cycle of the stagbeetle
as a multiparameter system
It is about the biggest beetle in Sweden, stagbeetle (ekoxe in swedish):Lucanus cervus
The size of the enlarged mandibles for the male are an important variable (parameter)
for the life cycle of the stagbeetle Lucanus cervus.
The male mandibles are large but weak; harmless for people.
The size of the mandibles vary greatly
from year to year and between different individuals for the same year.
The female has "normal" mandibles but on the other side they are strong and can hurt people.
The life cycle spans five to six years.
The adults live for aboute 20 days in June/July(Sweden) in their last year.
The males climb oaks and when they reach the upper leaves start to fly and
mostly land in the lower part of the same oak,
but sometimes they land on another one, up to a hundred meters away,
and start to climb again on a new track.
If a male, when climbing, meets another male the two males start to fight with their mandibles.
But the fight is harmless;
the outcome being that one of them will fall down to the ground
and has to restart his part of the "game" from the very beginning.
A climbing male to the left and a leafless oak to the right to show the geometry.
Up to this point the last year of the life cycle for the males is like the game:
"Fia med knuff" in Sweden,
"Mensch, Ärgere Dich Nicht" in Germany,
Ludo in (Norway, Demmark... England),
"Les petits chevaux" in France,
"Non ti Arrabbiare" in Italy;
the game is not common in USA
but has the name, Parcheesi.
Originally it was derived from Pachisi, which originated in ancient India.
The females also climb up and fly down; but more passively and in addition they create a soft clicking sound.
The creation mechanism of the sound is visible in the movie below; relative movement between segments.
The meaning of the sound is not understood. It could be for attraction or for avoidance.
The latter could be the case for the larvae; to spread out in the wood they are eating.
When a male and female meet they come together
and the female will afterwards fly away and start to prepare herself for laying the eggs.
The stagbeetle-system, including the evolution, is probably simple enough to be studied as a multparameter system
with different time scales as an abstract plasma!.
The pictures were taken in Ekeberg, Blekinge, Sweden; July 1997 (Christer Juren).
More to come