Insects are the most speciose group of animals, but the phylogenetic relationships of many major lineages remain unresolved. We inferred the phylogeny of insects from 1478 protein-coding genes. Phylogenomic analyses of nucleotide and amino acid sequences, with site-specific nucleotide or domain-specific amino acid substitution models, produced statistically robust and congruent results resolving previously controversial phylogenetic relations hips. We dated the origin of insects to the Early Ordovician [~479 million years ago (Ma)], of insect flight to the Early Devonian (~406 Ma), of major extant lineages to the Mississippian (~345 Ma), and the major diversification of holometabolous insects to the Early Cretaceous. Our phylogenomic study provides a comprehensive reliable scaffold for future comparative analyses of evolutionary innovations among insects.

The aquatic leaf beetle species Macroplea mutica and M. appendiculata (Coleoptera, Chrysomelidae, Donaciinae) differ in their use of Myriophyllum spicatum as a host plant As a contribution to the continuing discussion of the ecological differentiation and stable coexistence of species, we investigated the extent to which the two sister species, Macroplea mutica and M. appendiculata, use the host plants Myriophyllum spicatum and Potamogeton sp. Specimens from four populations differing in host plant experience were used for behavioural observations. Both species did not feed on Myriophyllum but on Potamogeton. Beetles kept on Myriophyllum or without plant lost weight, while those on Potamogeton maintained or increased their weight. Only M. appendiculata laid eggs on this plant, as well as on Potamogeton, where M. mutica exclusively oviposited. In choice experiments, all larvae preferred the roots of Potamogeton over Myriophyllum for attachment (also the M. mutica larvae that had been collected from Myriophyllum). The data are discussed in the light of the unusual occasional occurrence of M. mutica on Myriophyllum and the speciation in the genus Macroplea.

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