Hi everyone,
Today we are going to be looking into the life of an alcon blue butterfly
(Phengaris alcon).
After mating, the females lay their eggs on marsh gentian, a blue-coloured
wildflower. The eggs can only be laid on these flowers, as this is what the
newly hatched caterpillars will eat. Although in some alp regions, they can
also be found on willow gentians, a close relative of the marsh gentian. Once
the caterpillars have hatched from the eggs, their main predator and danger
are the ants that swarm below. But high on their plant homes, the caterpillars
are safe.
However, this isn't where the alcon blue caterpillars are going to stay
forever. Eventually, they drop down to the ground using silk strings. With no
protection, they are soon dragged off by the ants. The most amazing part is,
the alcon blue caterpillars give off the same scent and chemicals as the ant
larvae. So the ants take the caterpillars back to their brood chamber, where
the caterpillars are quickly fed just like the ant larvae. The caterpillars
will even make similar sounds to that of the queen ant, to receive even more
attention. Due to the immense amount of food, the caterpillars become massive
and well-developed.
The caterpillars will stay in the ants' nest for almost two years. Then they
pupate. Fast forward a few weeks, and an adult alcon blue butterfly emerges.
They now must quickly leave the ants' nest and climb up a nearby grass stem to
unfold their wings before flying away to find a mate.
This life cycle saves the blue alcon butterfly from a lot of work and ensures
that no caterpillars die from starvation. However, if either the ants or the
marsh gentian were to go extinct, so would the alcon blues. In other words,
they aren't adaptive and in a fast-changing world, this might be their
downfall.
Some ant colonies change the scent their larvae give off to stop the blue
alcon's from getting in. This has sometimes been called an 'arms race' between
the butterflies and the ants. Depending on location, the butterflies will use
different ant species as hosts, all from the genus 'Myrmica'.
An interesting phenomenon is when the ''Ichneumon eumerus'' wasp tracks down
the blue alcon caterpillars that are staying in the ants' nests. Once the
wasps have found the blue alcons, they spray the nearby ants with a chemical
that makes them attack each other. In all the confusion, the wasp injects the
caterpillars with its eggs. When the caterpillar pupates, the wasp larvae feed
on the chrysalis from the inside.
Despite all of this, blue alcon butterflies are classified as
Least Concern
and have habitats dotted around Europe and northern Asia.
Your Green World Blog Team💚
Sources:
Documentary: Our Planet (2019) voiced by David Attenborough E5 From Deserts to
Grasslands 32:00 (Available on Netflix and Youtube)
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