_Experimental hosts._--_Blatta orientalis_, _Blattella germanica_, and _Periplaneta americana_, U.S.A. (Cunliffe, 1952). Eggs of this mite (fig. 4) are usually laid indiscriminately in the rearing cages, rarely on the host. Eggs are coated with a sticky secretion which enables those laid on the host to adhere. Hatching occurs in 6-11 days at 90-95° F., and in 9-11 days at 80° F. The newly hatched larva starts to feed immediately on the cockroach. Larval stage lasts 4-6 days, rests 2-3 days, and molts. During the single nymphal instar, the mite feeds on the host and moves about for 6-7 days. The mite then rests 3-4 days before molting. Entire life cycle covers a period of 28-32 days. Adult mite lives 2-3 weeks, during which time it can produce 2-3 batches of from 1 to 20 eggs; the usual batch is about 12 eggs. The mites are unable to live on cockroach feces, cast skins, or dead cockroaches. Mites died within 4-5 days unless live cockroaches were supplied. Parasitism was proved by detecting radioactivity in mites that had fed on cockroaches which had been previously fed radioactive NaCl (Cunliffe, 1952). The mites can destroy laboratory cultures of cockroaches (Piquett and Fales, 1952; Edmunds, 1953a). A cockroach attacked by 25 mites succumbed after about an hour, falling on its back; it died after 5 hours (Cunliffe, 1952). When found in homes and offices, these mites are an indication of the presence of cockroaches; the mite has been twice accused of biting people (Baker et al., 1956). RECORDS OF UNIDENTIFIED MITES _Natural hosts._--_Aglaopteryx facies_, Puerto Rico (Seín, 1923): Four red "tick" nymphs found under wings of female. _Blaberus craniifer_, U.S.A., Florida (Hebard, 1917): "A number of lice [mites] are present on many of these specimens [28[F][F]]." _Blaberus discoidalis_, adventive from West Indies, taken in Scotland (Stewart, 1925): A considerable number of mites were all over the body and hind wings. _Blatta orientalis_, Germany (Cornelius, 1853): Ex sexual organs of male. _Blattella germanica_, U.S.A., in laboratory (Parker, 1939): Under conditions of high humidity, the cockroaches became heavily infested with mites. In cages where the infestation was heavy, an abnormally large number of females dropped their oöthecae, and the percentage of eggs hatching was low. _Parcoblatta uhleriana_, U.S.A., North Carolina (Hatcher, 1939): Hypopi of mites were found deeply embedded in the fat body of two individuals. Mites in the hypopial stage attach to insects by which they are dispersed. Hypopi have been found in the gill chambers of a mollusk and in the gonads of a millipede (Baker and Wharton, 1952). _Periplaneta americana_, U.S.A., in laboratory (Fisk, 1951): The insects were sluggish and molted with difficulty. Gold Coast Colony (Macfie, 1922): Larvae of a tarsonemid mite were found in the feces.