McClure (1936) obtained a large nest of _Vespula maculata_ (Linnaeus) [= _Vespa maculata_] in March in Illinois. In it were living 65 nymphs of _Parcoblatta pensylvanica_, 3 spiders (_Philodromus pernix_ Blackwall), 2 immature spiders (_Drassus_ sp.), and 6 mites. Balduf (1936) observed four individuals of _Parcoblatta pensylvanica_ in a nest of _Vespula maculata_; he suggested that they probably fed on dead bodies and organic wastes of the wasps. However, Rau (1940) has observed this cockroach devour a _Polistes_ larva in its cell. Although we do not imply that a commensal relationship exists between _Parcoblatta_ and the wasp, it is well to recall a statement by Rothschild and Clay (1957): "A commensal relationship is potentially even more dangerous than a merely social tie, for by nature it is more intimate. The closer the association, the more easily is the balance upset. One partner can then suddenly take a mean advantage of the other." Cockroach nymphs may enter bees' nests where, according to Imamura (_in_ Sonan, 1924), they do not feed on honey or pollen but presumably feed on excreta of bees or anything scattered by bees in their nest; the bees are not disturbed by the cockroaches. Cockroaches that have been found in the burrows of vertebrates are listed on pages 23-25. Paulian (1950) found immature cockroaches in the nests of birds (Ploceinae) in Madagascar and Ivory Coast. All nests of _Fondia_ sp. examined in Madagascar contained many cockroaches, and Paulian believed that the blattid was a species peculiar to the nests of birds. Three nests of _Ploceus_ sp. in Ivory Coast yielded one or two cockroaches each in association with more numerous mites, Psocoptera, Heteroptera, beetles, and lepidopterous larvae (Delamare, Deboutteville and Paulian, 1952). These last cited workers also found four cockroaches in a nest of _Estrildine_ sp., and two in a nest of an undetermined bird, all in association with other arthropods. Moulton (1912) observed large numbers of _Symploce cavernicola_ and _Periplaneta australasiae_ swarming in soft bird guano on the floor of caves in Borneo. Abdulali (1942) found in India many _Periplaneta americana_ in caves containing the edible-nest swift; there was no indication of association of the cockroaches with the birds. Danforth (_in_ Wolcott, 1950) reported finding large numbers of _Aglaopteryx facies_ "in the nests of the grey kingbird, in the region of the Cartagena Lagoon [Puerto Rico], 'living among the twigs.'" In Trinidad, Kevan found a male of _Blaberus discoidalis_ in a bird's nest (Princis and Kevan, 1955).