It is likely that the smaller wasp egg parasites are more effective than the evaniids in controlling cockroaches. Only one evaniid develops in a parasitized oötheca, but many individuals of the other wasps develop in one oötheca and the number of females that emerge is usually large. However, Cameron (1957) concluded that, with a parasitism rate of 25 to 29 percent and three to four generations a year, against one or less for the host, Evania appendigaster in the areas where it is established is a valuable control agent.
The use of specific egg parasites to control cockroaches has not been attempted extensively. Cros (1942) liberated a species of Tetrastichus (=Eulophus sp.; see p. [254]) in his home in Algeria to control the oriental cockroach; as far as we know, he did not report the parasite's effectiveness in reducing the cockroach population. According to Zimmerman (1948) Comperia merceti, when accidentally imported, practically wiped out Supella supellectilium in parts of Hawaii; he claimed to have controlled the brown-banded cockroach in a store building with this parasite. In some parts of Honolulu, almost 100 percent of the oöthecae of this cockroach were parasitized (Zimmerman, 1944). We (1954b) ran some simulated field tests in which we liberated Tetrastichus hagenowii in rooms artificially seeded with oöthecae; from 28 to 83 percent of American cockroach oöthecae and 56 percent of oriental cockroach oöthecae were parasitized during these tests.
Evania appendigaster was introduced from Hawaii into Canton Island in 1940 against Periplaneta americana, and it has become established (Dumbleton, 1957). This parasite was also successfully introduced into Samoa (Dumbleton, 1957).
Cockroach-hunting wasps.—An earnest attempt has been made to establish in Hawaii wasps that prey on cockroaches. Just how effective these wasps are in controlling cockroaches is still unknown. Dolichurus stantoni was introduced from the Philippines in 1917 and spread to several of the Islands (Swezey, 1920, 1921; Williams, 1944). Bridwell (1920) stated that as a result of this introduction there was a great decrease in cockroaches of the genus "Phyllodromia." A number of Podium haematogastrum from Brazil were liberated in Honolulu (Williams, 1925) but did not become established (Williams, 1928). The effectiveness of Podium was questioned by Williams (1928) who observed that Podium "destroyed innumerable Blattidae, which nonetheless swarmed in their neighborhood, and I must confess from my observations on the various cockroach-hunting wasps that the blattid more than holds its own alongside its enemy."
Introductions of Ampulex have proved more successful. Ampulex canaliculata was introduced into Hawaii from the United States (Williams, 1928a, 1929). Williams also introduced A. compressa into Hawaii in 1940, and the species was reared in large numbers for distribution (Pemberton, 1942). A. compressa has since become established on most of the Islands (Pemberton, 1945a, 1947; Williams, 1946; Van Zwaluwenburg, 1950). The thousand of A. compressa now found in the Hawaiian Islands are all descendants of three wasps captured in Noumea, New Caledonia (Williams, 1944). According to Williams (1941), the number of cockroaches was noticeably reduced at the University of Hawaii poultry farm, where some A. compressa were released. Pemberton (1953) believed that this wasp has become sufficiently abundant to be of definite value. Simmonds (1941) recommended importing A. compressa into Fiji for cockroach control. A. compressa was introduced from Hawaii into Guam in 1954 against Periplaneta americana and into the Cook Islands in 1955 against Periplaneta spp.; it is not yet known whether the parasite became established in either place (Dumbleton, 1957).
VERTEBRATES
... on conserve avec soin les crapauds dans les maisons, et que les dames les tolèrent, même sous leurs robes, en raison de leurs continuels services, car ils se promènent sans cesse à la recherche des Kakerlacs.
Girard (1877)
Toads.—Bufo marinus was first introduced into Puerto Rico from Barbados in 1920 to reduce several major insect pests including cockroaches (Leonard, 1933). It was introduced from Puerto Rico into Hawaii by C. E. Pemberton in 1932 where it rapidly became established; it has since been distributed throughout the Pacific area. B. marinus is one of the world's largest toads; it attains a body length (exclusive of the hind legs) of 7 to 9 inches (Oliver, 1949) and has been kept alive for more than 11 years in captivity (Pemberton, 1945). Alicata (1938) placed giant toads in a fenced area in Hawaii containing an infestation of Pycnoscelus surinamensis; after 24 hours the toads were dissected and each was found to have eaten from 11 to 25 cockroaches. Illingworth (1941) found that 40 to 90 percent of 53 stools of this toad in Hawaii contained remains of P. surinamensis. Alicata (1947) recommended the maintenance of B. marinus in poultry yards to reduce the population of P. surinamensis, the vector of the chicken eye worm.