The extent of host selection varies among these parasites; some species will oviposit into the eggs of more than one species of cockroach, but others show some degree of host specificity. Positive selection of specific hosts by certain parasites appears in correlative data from different investigators on pages 235 to 254. There is a small body of data that shows nonacceptance of certain hosts by some of these wasps. For example, _Comperia merceti_ would not parasitize eggs of _Blatta orientalis_ or _Periplaneta americana_ in the laboratory (Lawson, 1954a). We (unpublished data, 1957) exposed a soft oötheca, recently removed from _Eurycotis floridana_, to _C. merceti_; no wasps developed; we had similar negative results with _C. merceti_ and oöthecae of _B. germanica_. We (1954b) could not induce _Tetrastichus hagenowii_ to parasitize eggs of _Blattella germanica_, _B. vaga_, or _Parcoblatta virginica_ in the laboratory. In our experiments, _T. hagenowii_ oviposited into eggs of _Supella supellectilium_, but the wasp eggs either failed to hatch, or if they hatched, the larvae died before completing development. Neither would _T. hagenowii_ parasitize eggs of _N. rhombifolia_ (Roth and Willis, unpublished data, 1957). _Anastatus tenuipes_ would not parasitize the eggs of _Latiblattella lucifrons_ Hebard, _Periplaneta americana_, _B. germanica_, or _B. vaga_ (Flock, 1941). _Anastatus floridanus_ would not oviposit into eggs of _S. supellectilium_ and only rarely into eggs of _P. americana_ or _B. orientalis_ (Roth and Willis, 1954a); in the laboratory, this wasp could not be maintained beyond one generation on the eggs of _P. americana_. Edmunds (1953b) could not induce _Prosevania punctata_ to parasitize eggs of _B. germanica_. Cros (1942) induced _P. punctata_ to oviposit into a mantid oötheca, but neither mantids nor parasite developed. COCKROACH-HUNTING WASPS A number of wasps of the families Ampulicidae, Sphecidae, and a very few species of Pompilidae have been found to provision their nests with nymphal or adult cockroaches. This habit of preying on cockroaches is primitive (Leclercq, 1954); Leclercq (personal communication, 1955) stated that this habit is always associated with the conservation of a number of structures considered as archaic from a purely morphological point of view. The records of wasps of the genus _Astata_ capturing cockroaches (e.g., Sickmann, 1893; St. Fargeau _in_ Sharp, 1899) "all trace back to a questionable record by Lepeletier (1841) which probably was a misidentification of the predator" (K. V. Krombein, personal communication, 1956). Marshall (1866) suggested that the braconid _Paxylomma buccata_ Bréb., which he found frequenting cockroach runs in Pembrokeshire, was parasitic on _Ectobius nigripes_ Stephens; however, this wasp is undoubtedly parasitic on ants, probably on ant larvae (Donisthorpe and Wilkinson, 1930).