Shaw (1925) claimed that _Supella supellectilium_ tended to oust _Blattella germanica_, but Pope (1953) thought it doubtful in Queensland. Wolcott (1950) stated that "The larger and more powerful domestic cockroaches, _Periplaneta americana_ (L.), _P. australasiae_ (F.) and _P. brunnea_ Burmeister have very definitely fallen behind in Puerto Rico in competition with the little German roach." Pessôa and Corêa (1928) observed that other species of cockroaches were rare in Brazil in houses that were infested with _Leucophaea maderae_. Lederer (1952) noticed that in the reptile house of the aquarium at Frankfort am Main _Blatta orientalis_ was obviously kept down by _Blattella germanica_, even before the appearance of _P. americana_. However, _B. germanica_ was not driven out of the reptile house by _P. americana_ although the populations of each fluctuated for about 22 years after the American cockroach had settled there; both species occupied separate resting places. Lederer further observed that within four years of the introduction of _P. americana_ into the crocodile house, none of the original infestation of _B. orientalis_ could be found; a small colony of _Pycnoscelus surinamensis_ in the reptile house was apparently also driven out by _P. americana_. Chopard (1932, 1938) stated that the oriental cockroach does not exist in company with _P. americana_ which very probably destroys it. Pettit (1940) kept _B. germanica_ and _P. americana_ together in a cage for several weeks but neither species gave any indication of feeding on the other. Froggatt (1906) stated that "It is probable that the advent of the larger and more formidable American cockroach into Australia has led to the retirement or destruction of our indigenous species" [presumably _Periplaneta australasiae_]. Tillyard (1926) noted that this statement is incorrect as neither species is native to Australia. Yet Shaw (1925) stated that in Australia "When both species live together in the same places, _australasiae_ Fabr. will probably be found gradually to displace _americana_ L." Local fluctuations in the relative abundance of these species could be a basis for such dissimilar observations. However, MacDougall (1925) observed that in the plant houses of the Royal Botanical Garden, Edinburgh, the Australian cockroach seemed to have overcome the American which had been more numerous in former years.