POLIOMYELITIS VIRUSES
* Lansing strain
Experimental vectors.—Blattella germanica, U.S.A. (Hurlbutt, 1949, 1950).
Periplaneta americana, U.S.A. (Hsiang et al., 1952).
* Brunhilde type, Minnesota and Mahoney strains
Experimental vectors.—Periplaneta americana, U.S.A. (Fischer and Syverton, 1951; Syverton et al., 1952).
* Columbia SK virus
Experimental vectors.—Periplaneta americana, Great Britain? (Findlay and Howard, 1951): Results with Blattella germanica were negative.
* Four unspecified strains
Natural vectors.—Blattella germanica and/or Blattella vaga, Periplaneta americana and/or Periplaneta brunnea, and Supella supellectilium, U.S.A. (Syverton et al., 1952; Dow, 1955; Dow in Roth and Willis, 1957a).