Some misconceptions or preconceived ideas on the history of the Insects

Abstract

The Hexapoda is the most diverse clade of the history of life. They cannot be considered as the oldest terrestrial animals and the first Hexapoda were small apterous animals of the Devonian soil fauna, apparently not very diverse and “dominated” by myriapods and arachnids at that time. Things dramatically changed during the Early Carboniferous with the appearance and the expansion of the winged insects. This crucial innovation allowed this clade to diversify in a spectacular way in the Late Carboniferous. The main clades were already present at the end of this period, viz. Palaeoptera, “Polyneoptera”, Paraneoptera and Holometabola. The latter two groups became truly diverse and began to dominate the animal kingdom after the major Permo-Triassic biodiversity crisis. Nevertheless a causal link is difficult to establish between the two phenomena. After the Triassic, all insect orders are present and many modern families are as old as the Jurassic, a situation completely different from that of the terrestrial vertebrates. The last major change in the hexapods took place about 100 Ma ago, and may be linked with the mid-Cretaceous angiosperm diversification, but apparently not with the supposed major crisis of diversity at the end of the Cretaceous.