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
The size of the enlarged mandibles for the male are an important variable
(parameter) for the life cycle of the stagbeetle Lucanus cervus.
male mandibles are large but weak; harmless for people.
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
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.
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
"Fia med knuff" in Sweden,
"Mensch, Ärgere Dich Nicht" in
Ludo in (Norway, Demmark... England),
"Les petits chevaux" in
"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
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
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
The pictures were taken in Ekeberg, Blekinge, Sweden; July 1997 (Christer
More to come
they have on the "Tree of Life" for Lucanidae
does Darwin say
More about the
My favourite beetles as
Please make some Auroral sketches
Children and the sun
My pictures from Olympus-Pen