Native Ectobius (Blattaria: Ectobiidae) From the Early Eocene Green River Formation of Colorado and Its Reintroduction to North America 49 Million Years Later

Ectobius kohlsi sp. n. and three undetermined species of the common Eurasian cockroach genus Ectobius Stephens, 1835 are reported from the lower middle Eocene of North America. This species indicates a cosmopolitan distribution of the genus during the mid Paleogene, and supports its current relict distribution in modern north-temperate and African ecosystems. When compared with the living species, E. kohlsi was either neutral or plesiomorphic in all characters, but exhibited a close relationship to the extant Ectobius kraussianus Ramme, 1923 Species Group in the identical structure of the pronotum. E. kohlsi also was similar to extant Ectobius ticinus Bohn, 2004, in the character of its wing venation (see Bohn 2004), in particular the forewing vein M, and to extant Ectobius vittiventris (Costa 1847) in details of forewing coloration. These latter two species are members of the Ectobius sylvestris Species Group (Bohn 1989). Ectobius balticus Germar et Berendt, 1856-a conspicuously dominant cockroach from mid-Eocene Baltic amber-also appears plesiomorphic in all characters despite being a few million years younger than E. kohlsi. One reason for the complete disappearance of this dominant genus from North America is the peculiar consequence that, after 49 million years, a cool-adapted Ectobius lapponicus (L.) was capable of being reintroduced to a significantly cooler North America than that its antecedents which inhabited North America during a warmer European Eocene. Modern E. lapponicus is synanthropic in North America, even though no synanthropism is recorded for this species in its native habitat throughout Europe.