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Text and photographs protected by Copyright © Adrian Hoskins 2007, and must not be published in part or in whole elsewhere without prior written permission from the author.
 
 
Mimicry

As discussed previously, unpalatable or toxic butterflies often have prominent patterns. Experiments have shown that some avian predators can memorise these patterns and learn to avoid eating similarly patterned species in the future.

Batesian mimicry

The 19th century naturalist Henry Walter Bates realised that many edible species had uncannily similar patterns to unrelated toxic species. An example is the male of the Amazonian species Patia orise ( Pieridae ), which bears a quite extraordinary resemblance to the toxic Glasswing Methona confusa ( Ithomiinae ). The female of Patia orise is totally different in appearance, and bears a strong resemblance to another toxic species Ituna ilione ( Danainae ).

Bates published a scientific paper in 1862, in which he theorised that palatable species occasionally produced mutant forms with visual characteristics similar to toxic species. He believed that they would therefore be less likely to be killed by birds, and would pass on their characteristics to their offspring. He proposed that as a result of further mutations over the millennia, that palatable species had evolved to become almost identical to the toxic species.

Perhaps the most well known example of Batesian mimicry is that of the Viceroy Limenitis archippus, which mimics the Monarch Danaus plexippus. There are countless other examples, including the many edible Dismorphia and Heliconius species which mimic toxic Ithomiines; and the palatable Papilio troilus which mimics the toxic Battus philenor.

Methona confusa, an unpalatable Nymphalid from the subfamily Ithomiinae. The butterfly contains toxins that are derived from it's caterpillar's foodplants, and from adult food sources such as Heliotropium and Eupatorium flowers.
A bird that has tasted this species is unlikely to attack anything that looks similar.
Patia orise, a remarkably similar edible Pierid species from the subfamily Dismorphiinae. This species has 6 legs, a shorter body, narrower forewings, much larger hindwings, and different venation.
 
Methona has 4 very long legs, drooping antennae, and a series of tiny white spots around the wing borders.

Müllerian mimicry

In 1879, Müller realised that many toxic or unpalatable species shared very similar patterns, and proposed that this was a form of evolutionary "cooperation" which increased the chances of each species avoiding attack. This is referred to as Müllerian mimicry, and is a very common phenomenon amongst the Ithomiinae and Danainae.

In cases of Müllerian mimicry, all of the species involved are inedible or toxic to birds and reptiles, and the commonest species in the group serves as the model for the others.

The Tiger Complex

A famous example of butterfly mimicry is the "tiger complex" - a group of about 200 mostly toxic species which all share a very similar pattern of orange and yellow stripes on a black ground colour. Any bird which suffers the unpleasant experience of tasting one member of the tiger-complex quickly learns to avoid attacking any similar looking species.
The tiger complex includes example of both Batesian and Müllerian mimics. These include the toxic Ithomiines Tithorea harmonia, Melinaea marsaeus and Forbestra equicola; toxic Danaines such as Lycorea pasinuntia, and smaller numbers of palatable Batesian mimics including Perrhybris pamela ( Pierinae ), Eresia eunice ( Nymphalinae )
Stalachtis calliope ( Riodinidae ), Consul fabius ( Charaxinae ), Heliconius ismenius
( Heliconiinae ) and Pterourus zagreus ( Papilioninae ).
 

Consul fabius, Charaxinae

Heliconius numata, Heliconiinae
The species in this group, despite being unrelated, all share a similar "tiger" pattern of orange bands or stripes on a blackish ground colour. Most also have elongated wings, creamy antennae, and a habit of fanning their wings to draw attention to themselves - advertising their toxic
( or supposedly toxic ) qualities to predators. Some species resemble each other so closely that even expert entomologists get fooled !
 

Tithorea harmonia, Ithomiinae

Mimicry, or coincidence ?

Although widely accepted, mimicry theories are not totally convincing.

Clearly mimicry can only evolve if the mimic and model spend their entire evolutionary history in the same habitat and geographical region. There are however many examples of strong similarities in colour and pattern amongst unrelated species from widely separated regions. Such similarities cannot be attributed to mimicry, so how did they come about ?

The biological mechanisms which generate wing patterns are fundamentally the same for all butterfly species. It is therefore reasonable to assume that similarities are very likely to occur amongst unrelated species, particularly where they co-exist in the same habitat and the mechanisms are affected by the same climatic and environmental factors. Equally it is likely that the common mechanisms will cause similar visual attributes to appear even in unrelated species in other parts of the world, although similarities will occur less often, as the environmental factors are different.

Mimicry of other insect Orders ( e.g. bees and wasps ) is an entirely different matter, as the biological mechanisms by which patterns and shapes arise are not shared. The fact that many harmless species of moths, beetles and hoverflies clearly mimic bees and wasps can surely only be attributed to the evolution or creation of such designs for the purpose of tricking natural enemies into believing that the moths can sting ! The 2 examples below, of Arctiid moths from Peru, are pretty convincing......

 
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Related subjects :
 
Taxonomy  - the classification and characteristics of butterfly families and sub-families.
Lifecycle - egg, caterpillar, chrysalis, adult butterfly, courtship, reproduction.
Parasitoids and Predators - of eggs, larvae, pupae and adult butterflies.
 
Text and butterfly photographs protected by Copyright © Adrian Hoskins 2007-2008, and must not be reproduced or published in part or in whole elsewhere in any form without written permission from Adrian Hoskins. Breach of copyright will be pursued by litigation.
 
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