Deceptive butterflies

Many butterflies we used to see as children at the meadows hide a [dirty] secret. One of the most beautiful and well known butterflies in Europe Large Blue or Arion Blue, scientific name Maculinea arion, is one of them.

The truth is all Maculinea butterflies (4 or 5 species according modern taxonomy) are deceptive creatures. It is hard not to notice the beautiful imago butterflies with navy blue or sky blue wings covered with tender black spots. Plus, Maculinea arion is fairly large species, the wing span of this species can rich 16-20 mm. Not surprising, Maculinea arion was in every naturalist collection of Victorian England. However, until late 70th little was known about their unique and fascinating life cycle. Their struggle for survival and the ways they took in their evolutionary history to turn the world around.

In  60th-70th scientist of Great Britain realized that Maculiena arion population is declining with deteriorating speed. At first collectors were to blame. In 1979 no Maculinea arion could be found on the Islands. By that time scientist already figured out that the main reason for extinction of this species is its exceptional sensitivity to the changing environment due to double specificity: the host plant which is very important for survival of the larvae during first three stages of the development and the ant host which ensures further development of the larvae in the ant nest. If either of these factors affected (plants due to early mowing before larvae left the plant; ants due to destruction of their habitat), the butterflies can not finish their cycle and population unavoidably will decline.

To be more specific, the adult Maculinea arion females lay their eggs only on specific plant, thyme, in the summer. The larvae stays on the flowers only three stages and while still very small eventually falls to the ground. The Maculinea larvae produce special chemicals and sounds to lure red ants and fool them into thinking the larvae is ant grub. The fooled ant following its instincts then carries the tiny larvae into its nest. The important point here is that Maculinea larvae can mimic only chemicals and sounds of certain red ant species, all other species will not be so easily fooled by these disguise, which means that only certain number of larvae has the chance for survival to adulthood – only those who ended up in the right nest of the right species. Ideally, the ants never discover that they have been fooled, and instead continue to protect the butterfly larvae for several months and feed them [or, in majority of cases, let the larvae to eat their own brood].

Maculine arion life cycle, from MacMan project.

Comments

  1. That’s so interesting – thanks for posting such detailed information about them. Reminiscent of their counterparts – the Cuckoo.

    • Yes, some scientists call Maculinea ‘cuckoo’ species, the only difference that larvae can switch between predatory and cuckoo behavior if necessary.

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