This consideration leads us to one of the most remarkable and fascinating features of 'ant-communities - the presence in the nests of insects and other small arthropods, which are tended and cared for by the ants as their " guests," rendering to the ants in return the sweet food which they desire.
Exoskeleton The outer cellular layer (ectoderm or " hypodermis ") of insects as of other Arthropods, secretes a chitinous cuticle which has to be periodically shed and renewed during the growth of the animal.
- A striking feature in the food-canal of the Hexapoda, as in other Arthropods, is the great extent of the " foregut " and " hind-gut," lined with a chitinous cuticle, continuous with the exoskeleton.
The Hexapoda, being aerial, terrestrial and fresh-water animals, are but occasionally preserved in stratified rocks, and our knowledge of extinct members of the class is therefore fragmentary, while the description, as insects, of various obscure fossils, which are perhaps not even Arthropods, has not tended to the advancement of this branch of zoology.
Relationships And Phylogeny The Hexapoda form a very clearly defined class of the Arthropoda, and many recent writers have suggested that they must have arisen independently of other Arthropods from annelid worms, and that the Arthropoda must, therefore, be regarded as an " unnatural," polyphyletic assemblage.
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