Synonymy.—Because of the war, Cros (1942) could not determine this insect specifically. He designated it provisionally and with reserve under the name Eulophus sp. However, Burks (p. c., 1956) stated that the species is most certainly a Tetrastichus from the description given; but, it is apparently not T. hagenowii because of its brilliant steel-blue color.
Natural host.—Blatta orientalis, Algeria (Cros, 1942): Adult behavior.—Mating began as soon as wasps emerged from an oötheca. Males mated repeatedly. Adults lived up to 5 days in summer and up to 12 days in fall. There were up to four generations per year in the laboratory. Oviposition.—Wasps oviposited into oöthecae 6, 22, 40, and 43 days old, and the parasites developed successfully. More than one female oviposited into the same oötheca. Oviposition was of long duration. Development.—From egg to eclosion took an average of 34 days in summer (range: 30-38 days, 5 oöthecae), and an average of 67 days in fall (range: 58-73 days, 3 oöthecae). An average of 55 parasites developed per oötheca (range 21-105, 5 oöthecae); over 130 wasps emerged from a sixth oötheca. Sex ratio.—10-20 ♀♀:1 ♂.
HOST SELECTION BY EGG PARASITES
The nature of the oviposition stimulus(i) for the wasp parasites of cockroach eggs is unknown. Edmunds (1954) noted that Prosevania punctata showed more interest in oöthecae that had been cemented to the substrate than in clean oöthecae that had simply been dropped. Cros (1942) experimented with two females of P. punctata to see if the wasps could find oöthecae that had been buried in sand by the oriental cockroach. After prospecting the sand with their antennae, the wasps dug deep excavations with their front legs but always mistook the location of the oöthecae. Cros suggested that the wasps were misled by the odor left in the jar by the cockroaches. It is quite possible that odor helps the wasp find the host oötheca.
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 We (unpublished data, 1957) exposed a soft oötheca, recently removed from Eurycotis floridana, to C. merceti; no wasps developed; we had similar negative results with C.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).
The wasps that are known to capture cockroaches, and summaries of their biology, are listed below.