The origin of the insect odorant receptor (OR) gene family has been hypothesized to have coincided with the evolution of terrestriality in insects. Missbach et al. (2014) suggested that ORs instead evolved with an ancestral OR co-receptor (Orco) after the origin of terrestriality and the OR/Orco system is an adaptation to winged flight in insects. We investigated genomes of the Collembola, Diplura, Archaeognatha, Zygentoma, Odonata, and Ephemeroptera, and find ORs present in all insect genomes but absent from lineages predating the evolution of insects. Orco is absent only in the ancestrally wingless insect lineage Archaeognatha. Our new genome sequence of the zygentoman firebrat Thermobia domestica reveals a full OR/Orco system. We conclude that ORs evolved before winged flight, perhaps as an adaptation to terrestriality, representing a key evolutionary novelty in the ancestor of all insects, and hence a molecular synapomorphy for the Class Insecta.

Article Citation: Wesley A. Powell, William E. Klingeman, Bonnie H. Ownley, and Kimberly D. Gwinn (2009) Evidence of Endophytic Beauveria bassiana in Seed-treated Tomato Plants Acting as a Systemic Entomopathogen to Larval Helicoverpa zea (Lepidoptera: Noctuidae). Journal of Entomological Science: October 2009, Vol. 44, No. 4, pp. 391-396. https://doi.org/10.18474/0749-8004-44.4.391

Favored for their rapid growth and brilliant fall color, maple (Acer spp.) trees are among the most commonly grown deciduous shade trees in urban lan