The wasp beetle with its distinctive black and yellow markings.
NATURE NOTESI SPOTTED this fearsome-looking insect in our garden recently, which I quickly discovered was not as alarming as it looked.
The wasp beetle is harmless and merely uses similar warning markings in order to provide itself with the protection from predators enjoyed by wasps.
This is called 'mimicry’ and, more specifically in relation to evolutionary biology, it is a form of 'Batesian’ mimicry.
Henry Walter Bates (1825-1892) was an English explorer and naturalist who spent many years in the Brazilian rain-forest and noticed certain harmless species appeared to adopt certain characteristics of other species, which were poisonous or otherwise distasteful.
This type of mimicry can take several forms: it may be the mimicry of a smell (or pheromone) or it may take the form of a similar defensive noise or call, or even a similar posture.
This behaviour of sending messages to potential predators is called 'aposematism’ and some species only transmit such signals when they are actually threatened. These signals will normally be energy-depleting, and it is therefore not in the interests of the prey to send them continuously.
Some animals will suddenly display a flash of warning colour, for example, or adopt a posture which makes them appear larger or more frightening. However, the adoption of a colour-scheme, which simply makes the animal look like a more dangerous species, is the most common and least taxing method.
Insects are particularly good at this; many insects have adopted the strategy of looking like wasps or bees, usually to benefit from the protection that it offers. However, sometimes mimicry can be used to the opposite end: making it easier for a predator to dupe its prey. Some parasitic wasps, for example, look like the ants that they parasitize to make entry into their nests easier. Certain types of fireflies emit pheromones mimicking those of the female of a similar species, attracting the males, which they then devour.
Mimicry adopted as protection can only be effective as long as there are fewer of the mimics than the species being imitated (usually referred to as the 'model’).
If the harmless mimic became predominant, predators would soon learn the warning could be ignored and the protection would be lost. However, the warning colours of black and yellow, or black and orange, are so prevalent that it must be assumed it is a very effective colour combination, offering either a real warning, in the case of species such as wasps, frogs and lizards — to name but a few — or a opportunistic one.
Other forms of mimicry exist. A German naturalist, Fritz Muller, who also spent considerable time in Brazil, identified a form of mimicry where two or more poisonous species, that may or may not be closely related but share one or more common predators, have come to mimic each other’s warning signals.
The most commonly cited example is the mutual or collaborative arrangement reached by two butterflies — the Monarch and the Viceroy. Superficially appearing similar, they also both happen to be noxious and thus both they and the predators benefit from the arrangement: the butterflies from the wider recognisability of the similarly-marked species, and the predators from being duped into eating something unpleasant.