ADVERTISEMENTS:
The following points highlight the two main types of mimicry. The types are: 1. Protective Mimicry 2. Aggressive Mimicry.
Type # 1. Protective Mimicry:
Protective mimicry is divisible into two categories:
(a) Concealing mimicry:
ADVERTISEMENTS:
Most of the protectively mimic forms exhibit devices of concealing themselves in order to escape the clutches of enemies. Some insects exhibit protective resemblances to objects of the surroundings in forms and colours. A crab, Cryptolithodes with its smooth rounded form, texture and colour of the body perfectly harmonises the white pebbles of the beach to such an extent, it becomes very difficult to detect them.
Some geometric! caterpillars rest in a position which mimic a twig of the tree on which they live. In another geometrid moth, Schizura nucronis such mimicry is reached to the peak 13 where not only does the rough-barked caterpillar resemble the twig perfectly but the adult also does (Fig. 4.7A).
Some walking-stick insects of the family Phasmidae, with their body, slow movement, attenuated appendages and matching colouration resemble dead or green twigs and leaves.
Most perfect example is the leaf insect called Phyllium, where the wings along with the flattened and expanded body and limbs are mostly green (Fig. 4.7B). An Indian butterfly (Kallima) resembles a dead leaf when it rests with folded wings (Fig. 4.7C).
(b) Warning mimicry:
Many remarkably mimic forms exhibit warning mimicry. These forms advertise coloured texture which are either distasteful or poisonous if devoured. Some of the deadly poisonous snakes belonging to the family Elapidae are brilliandy coloured. Many poisonous coral snakes are mimicked by other harmless snakes of different genera.
A host of imitators are present amongst the insects. Amongst the butterflies there are many forms which mimic other distasteful forms. The most remarkable example is Basilar- chia archippus, which are highly palatable for the insectivorous birds, imitate the Anosia plexippns an inedible form.
Thus a relatively palatable species gets advantage from the predators, if it resembles a warningly coloured inedible species. This ‘false warning colouration’ is termed as the warning mimicry of Batesian type. If two of unpalatable species resemble each other, is called Mullerian mimicry. Mullerian mimicry is advantageous for both but Batesian mimicry is good only to the edible species.
Type # 2. Aggressive Mimicry:
This is the characteristic of some carnivorous forms. Spiders are the typical examples. In most cases the yellow body harmonises so perfectly with the colour of the flower upon which they rest that they become invisible for the visiting insects which constitute the spider’s prey.
Some spiders resemble an orchid blossom very closely in colour and forms which act as a lure. Similar phenomenon is observed in some African lizards where a patch of brilliant colour in the corner of the mouth is an alluring one.
Mimicked forms of animals are usually defenseless and this mechanism of imitating others is a highly adapted feature and at the same time has great survival value. Opinions differ as regards the origin of mimicry in animal kingdom.
It has been suggested by many that mimitic forms may have arisen as drastic mutations. Whatever the causes may be, it is quite suggestive to regard that Natural Selection plays the greatest role in the production of mimicry in animal kingdom.
