John Bebbington (FRPS), 8th February 2011
Investigating Identity Theft:
Mimicry in Land Invertebrates
John Bebbington is an expert on both entomology and photography. His insights into invertebrate mimicry were illustrated by stunning slides and we were treated to a comprehensive introduction to this unfamiliar world.
A moth's job is to survive two or three nights in order to mate. If it has done this it has been a success. John's restatement of the operation of Natural Selection lay at the heart of all the examples he showed us. Darwin's model of sexual reproduction leading to genetic variation and selective survival is the driver of the amazing range of camouflage, poison and subterfuge used by insects and other invertebrates.
By using camouflage the creature is able to conceal itself from potential predators by taking on the appearance of natural objects, either by blending in with the background on which it sits (the different colour forms of the Peppered Moth are a well-studied example) or, like certain caterpillars, by actually adopting the appearance of natural features such as twigs - birch, sallow and dogwood each acting as models for different species.
Mimicry on the other hand is a strategy whereby the creature adopts the appearance or behaviour of another species to protect itself from attack. Often this takes the form of one insect mimicking the coloration of a species which the predator has already learned to avoid because it is distasteful or even poisonous. Rather than trying to hide themselves these creatures often proclaim their in-edibility by prominent warning colours such as yellow and black stripes (wasps, bees and some caterpillars) or bright red colouring (burnet moths and cinnabar moths). Often these poisons are derived from the plants on which they feed, ragwort for example being a source of cyanide.
Aggressive mimicry is an interesting variation in which evolution has led to some predators using mimicry in order to catch their prey. So the crab spider ambushes its prey by taking on the form or colour of a plant to conceal itself and there is a variety of wasp which taps on a spider's web in such a way as to dupe the spider into thinking some prey has become enmeshed. It comes to investigate and duly falls prey itself.
I'm sure John would not object to the observation that the behaviour of entomologists can be at least as interesting as the creatures they study. At the age of two he was so attracted to a bee that he reached out for it, and it stung him. Rather than being permanently put off he was hooked for life! In later years he accidentally (!) cut a cinnabar moth caterpillar in half and decided to taste the resulting fluids. These proved to be so vile that a whole packet of extra strong peppermints was required to mask the taste. The famous entomologist Lady Miriam Rothschild tried a similar experiment on herself when in her nineties by rubbing some cinnabar fluid into a cut on her arm. Her heart rate doubled in fifteen minutes and she earned a severe telling off from her doctor.
Our thanks go to John for a splendid set of slides and an entertaining account
of this important branch of evolutionary studies.
John's suggestion for further study of this intriguing topic is to go online and track down the Wikipedia article on Mimicry.