Zeitschr. wiss. Zool. xxxv. 1881, Pl. IV. fig. 6.
Rep. of the Entomologist, 1886, p. 510, Washington.
Insectes fossiles des temps primaires, 1893, p. 38.
P. ent. Soc. London, 1866, p. lxv.
For a history of this complex question, see Gosch, Naturhist. Tidskr. (Rk. 3) vol. xiii. 1881; and also Brauer, Sitzb. Ak. Wien, lxxxv. 1882.