Davis (in Rehn and Hebard, 1914a) stated that "At Punta Gorda [Florida] there was a vacant house at the end of the town frequented at night by a Nanny and Billy goat, and on warm evenings many Periplaneta australasiae would run about on the piazza floor and on the sides of the house. They were seen feeding on the excrement of the goats and were no doubt to a great degree dependent upon them." This is another example of a coprophagous insect that has taken advantage of a particular situation favorable to its survival. Similar associations exist in which many of the domiciliary cockroaches feed on the feces of man and domestic and other animals (Roth and Willis, 1957a).
[XVI. COCKROACHES AS PREDATORS]
INTERSPECIES PREDATION
Tepper (1893) made the broad statement that the majority of Australian and Polynesian cockroaches appear to be wholly carnivorous, eating other insects, eggs, and larvae. He stated that, because of their voracity and cannibalistic tendencies, the carnivorous species lead more or less solitary lives so that one rarely meets several in close proximity; they are never very numerous at any time because the stronger devour the weaker in the absence of other prey. Tepper stated that Australian species of Ischnoptera hunt for their prey among the foliage of shrubs, and that Australian species of Cutilia [= Drymaplaneta, Hebard (1943)] run about actively on the surface, or ascend shrubs and trees in quest of living insects and therefore are highly beneficial. Tepper (1894) also stated that Geoscapheus robustus ate earthworms, grubs, and caterpillars. Froggatt (1906) and Marlatt (1915) attributed to Tepper the statement that cockroaches, like Epilampra notabilis, which are found out-of-doors in Australia, are carnivorous and feed on caterpillars and other soft-bodied insects; but Froggatt (1907) believed that this alleged behavior needed confirmation.
A number of observations have been recorded which indicate that sometimes cockroaches may be predatory. According to Ealand (1915), nymphs of the cockroach Pseudomops cincta fed on the Argentine ant Iridomyrmex humilis. In the laboratory, Eurycotis floridana has been observed to catch and devour the wasp Anastatus floridanus which parasitizes the eggs of Eurycotis (Roth and Willis, 1954a). Parcoblatta pensylvanica was observed devouring a larva of Polistes sp. in its cell in a deserted wasps' nest (Rau, 1940). Brigham (1866) saw a cockroach kill and eat a centipede four or five inches long. Annandale (1910) described the destruction in Calcutta of termites by Periplaneta americana. During a heavy rain storm many termites flew into the dining room and were set upon by the cockroaches which seized them with their mandibles and began to gnaw their abdomens. If disturbed, the cockroaches carried the termites away in their mandibles without using their legs to seize, hold, or carry the prey. Sometimes only the abdomen, but other times the whole body with the exception of the wings, was devoured. Perhaps this observation led Allyn (Anonymous, 1937) to theorize that, first, cockroaches could eradicate termites from houses, and then the blattids in turn could be eliminated. Falls (1938) has pointed out the unfeasibility of this idea. Blattella vaga has shown some tendency to eat plant lice (Flock, 1941a). Certain small cockroaches found beneath cane leaf-sheaths, in the Philippine Islands, preyed in part upon leafhoppers (Uichanco, in Williams et al., 1931).
Takahashi (1924) stated that the American cockroach will eat the eggs of the hemipteron Cantao ocellatus (Thunberg). Cunliffe (1952) observed mite-infested cockroaches (Blatta orientalis, Blattella germanica, and/or Periplaneta americana) dislodge and eat the mite Pimeliaphilus podapolipophagus. Sonan (1924) reported that cockroaches (P. americana and P. australasiae) devoured the egg clusters and first instar larvae of Prodenia litula and the first instar larvae of Attacus atlas which were being reared in the laboratory. Lederer (1952) stated that Periplaneta americana ate reptile eggs in the aquarium at Frankfurt am Main. Pettit (1940) stated that cockroaches "are said to have destroyed a large colony of dermestids used to skeletonize carcasses at the University of Kansas."
DeFraula (1780) believed that his silent "gryllon" [obviously Blatta orientalis from his drawings; see Willemet (1784)] was the enemy of the chirping species of cricket, because after the cockroach became established in his home he no longer heard crickets chirping. Gilbert White (1905 ed.), writing in England in the late 18th century, stated that "Poda says that these [Blatta orientalis] and house crickets will not associate together; but he is mistaken in that assertion"; however, in August 1792 White noted that "Since the blattae have been so much kept under, the crickets have greatly increased in number." For several years Jolivet (1950) had observed changes in a mixed population of Blatta orientalis and Acheta domesticus in an old kitchen in France. He suggested that the cyclical fluctuations in the relative abundance of the cockroaches and crickets might be caused by reciprocal predatism with one species more susceptible than the other at certain stages. Mallis (1954) has stated that crickets prey on other insects as well as on one another. Lhéritier (1951) had also observed crickets becoming rare in bakeries in France, having been superseded everywhere by B. orientalis; however, he doubted that Jolivet's hypothesis was the correct explanation and suggested that the higher optimum temperature requirements of crickets might be the regulating factor. Lederer (1952) stated that the number of crickets decreased in the aquarium buildings at Frankfurt am Main as the population of American cockroaches increased.
Platyzosteria novae seelandiae was found under the bark of trees in New Zealand devouring bugs (Walker in Shelford, 1909b).