As stated in my published note, the roaches were at first classified to genus only. The 83 _Periplaneta_ subsequently identified to species represented 28 different collections, 11 from houses and 17 from privies, all in Pharr, Texas. Tabulation of the data shows first that _P. americana_ was taken only once in a house and that _P. brunnea_ was taken only 4 times in privies. Of course this distribution greatly reduces the probability that they would be caught together, and it is not surprising that _P. americana_ was trapped alone in the single house collection. _P. brunnea_, however, was trapped with _P. americana_ 2 of the 4 times it occurred in privy collections. To investigate the occurrence of _Periplaneta_ with and without _Blattella_, an analysis has been made of 560 trap collections taken in 40 houses and 40 associated privies in Pharr, Texas, in weekly intervals (from May 14 to June 23 [1948]). In the houses, _Periplaneta_ and _Blattella_ were caught in the same jar 26 times, _Periplaneta_ alone 12 times, _Blattella_ alone 83 times, and neither genus 159 times. In a fourfold table, the value of chi-square (14.7) is significant and indicates that the frequencies are not proportional. The number of times _Periplaneta_ and _Blattella_ actually occurred together (26) is, however, much larger than the expected number calculated from the row and column frequencies (14.8). In the privies, _Periplaneta_ and _Blattella_ were caught in the same jar 9 times, _Periplaneta_ alone 50 times, _Blattella_ alone 18 times, and neither genus 203 times. In a fourfold table, the value of chi-square (1.95) is not significant but the same type of disproportion is evident and the expected frequency of both genera in one trap is 5.7, lower than the actual frequency of 9. Both immature and adult roaches are included in this analysis. The above evidence would be more satisfactory if based on more extensive data. There is also a possible objection in that the traps were operated for at least overnight, during which time one species could theoretically supplant another. Of course, it is doubtful that there is anything involved here like territory (in the ornithologists' sense). On the other hand, it is well to consider that _Periplaneta_ and _Blattella_ are both likely to be more abundant in the same type of favorable location and that this factor might offset in part some direct antagonism between the species. The only known specimen of _Ischnoptera podoces_ was captured in company with the type series of _Cariblatta nebulicola_, in dead leaf litter in Jamaica (Rehn and Hebard, 1927). In Florida _Periplaneta australasiae_ was often taken in company with _Pycnoscelus surinamensis_ and _Eurycotis floridana_ (Blatchley, 1920). INTERSPECIES ANTAGONISM