Why did insects win?

It basically starts from this blog post. The question is: why are Insecta the most diverse group of arthropods, if not of living beings, on Earth's land, while Arachnida and other arthropod groups aren't?

Here I collect some material for further posts on the subject.

Sources

Evolution of Arthropoda

• Marine evolution of Arachnida: "The oldest known scorpions lived around 430 million years ago in the Silurian period, on the bottom of shallow tropical seas.[15] These first scorpions had gills instead of the present forms' book lungs." ( Scorpion )

• Recent evidence for Pancrustacea hypothesis based on nuclear genes phylogenies: Regier et al. 2010

• Rota-Stabelli et al. 2010, mitochondrial genomes from several arthropoda, further Pancrustacea evidence.

Genes in evolution of arthropod body plans

• 1995 landmark paper] on crustacean Hox genes vs insect Hox genes, enlightening
• Book that sounds extremly interesting.

Evolution of insect flight

Wings as primitive tracheal gills: Evolution_of_insects#Origin_of_insect_flight

Evolution of metamorphosis

• "The evolution of complete metamorphosis in insects is a key innovation that has led to the successful diversification of holometabolous insects," Suzuki et al. (molecular biology of pupa)

Hypothesis

• The Pancrustacea hypothesis is intriguing because Crustaceans show also considerable diversity. Clades away from Pancrustaceans show less diversity? Measurement of morphological characters?