The negative impact of cockroaches introduced into non-native habitats is well documented. The handful of species that have invaded the man-made environment have had enormous economic significance as pests, as sources of allergens, as potential vectors of disease to humans and their animals, and as intermediate hosts for some parasites, such as chicken eye-worms. Exotic cockroaches have also been introduced into natural non-native ecosystems like caves (Samways, 1994) and islands, such as the Galapagos (Hebard, 1920b). In a survey of La Réunion and Mayotte in the Comoro Islands, 21 cockroach species were found, with introduced species more common than endemic species that use the same habitats. The abundant leaf litter and loose substrate typical of cultivated land was favorable habitat for the adventive species, particularly in irrigated plots (Boyer and Rivault, 2003). The Hawaiian Islands have no native cockroaches, but 19 introduced species (Nishida, 1992). Periplaneta americana has invaded a number of Hawaiian caves, and is thought to have contributed to the decline of the Kauai cave wolf spider (Adelocosa anops) by affecting its chief food source, cave amphipods. The cockroach opportunistically preys on immature stages of the amphipods, and competes with older stages at food sources (Clark, 1999). In Florida, laboratory studies indicate that the Asian cockroach Blattella asahinai may disrupt efforts to control pest aphids with parasitic wasps by feeding on parasitized aphid "mummies" (Persad and Hoy, 2004). Although this problem occurred primarily when the cockroaches were deprived of food for 24 hr, the high populations of Asian cockroaches that can occur in citrus orchards (up to 100,000/ha) (Brenner et al., 1988) guarantee that some are usually hungry.
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