Other Roles

Cockroaches are part of the guild of arthropods that provide waste elimination services; they feed on the fecal material of animals in all trophic levels (Roth and Willis, 1957). While this behavior is most often noted in relation to disease transmission by pest species, it is likely that cockroaches also contribute to the rapid processing of excrement in natural settings (Fig. 5.2). Cockroaches habitually found in bird nests, mammal burrows, and the middens of social insects provide nest sanitation services for their hosts. MacDonald and Matthews (1983) suggest that nymphs of Parcoblatta help prolong the colony cycle of southern yellowjackets (Vespula squamosa) by scavenging colony debris and keeping fungal and protozoan populations suppressed. Cockroaches (probably Peripla-neta fuliginosa) are frequently found in honeybee hives in North Carolina; their role in hive sanitation merits further investigation (D.I. Hopkins, pers. comm. to CAN).

In addition to acting as predators, prey, and regulators of microbial processes, cockroaches have ecological relationships with a variety of micro- and macrofauna. These include ecto- and endoparasites, parasitoids, and commensals (mites, for example). The burrows and tunnels of cockroaches that excavate solid substrates often serve as shelter for many additional tenants. The burrows of M. rhinoceros harbor a complex of other cockroaches (Calo-lampra spp., among others), beetles,silverfish, centipedes, frogs, and moths (Park, 1990; Rugg and Rose, 1991). One scarab (Dasygnathus blattocomes) has been collected nowhere else (Carne, 1978). Salamanders, centipedes, ground beetles, and springtails are frequently found in the galleries of C. punctulatus (Cleveland et al., 1934; CAN, un-publ.).

Within the human realm, cockroaches have both cultural and scientific significance. Several species are used as pets and pet food (McMonigle and Willis, 2000), and because they are robust under taxing conditions they make excellent fish bait. Urban pests serve as ideal subjects for a wide range of scientific studies. They are easily fed on commercially available pet chow, do not mind a dirty cage, withstand and even thrive under crowded conditions, and are prolific breeders. The relatively large size of some (e.g., Periplaneta) facilitates tissue and cell extraction, and their sizable organs are easily pierced with electrodes or cannulae. The cockroach nervous system is less cephalized than in many insects, making these insects excellent experimental models in neurobiology; two volumes have been written on the subject (Huber et al., 1990). Their overall lack of specialization makes them ideal for teaching students the basics of insect anatomy. They also readily lend themselves to laboratory experiments on the physiology of reproduction, nutrition, respiration, growth and metamorphosis, regeneration, chemical ecology, learning, locomotion, circadian rhythms, and social behavior (Bell, 1981, 1990). Therapeutic concoctions that include cockroaches are frequently cited in medical folklore, and their use as a diuretic has received some clinical support. Roth and Willis (1957) list 30 specific diseases and disorders where cockroaches have featured in treatment. When American jazz legend Louis Armstrong was a child, his mother fed him a broth made from boiled cockroaches whenever he was ill (Taylor, 1975). In southern China and in Chinatown in New York City, dried specimens of Opisthoplatia orientalis are still sold for medicinal purposes (Roth, 2003a),and Blatta orientalis is marketed on the Internet as a homeopathic medicine. Cockroaches produce a wide range of phero-mones and defensive compounds, and may be rewarding subjects for pharmaceutical bioprospecting. Given the close association of cockroaches with rotting organic matter, a search for antimicrobials may be particularly fruitful (Roth and Eisner, 1961). The secretions used by some oviparous species to attach their oothecae to objects have been likened to superglue, as attempting to remove the egg cases either ruptures them or also pulls up the substrate (Edmunds, 1957; Deans and Roth, 2003). Cock roach guts, like termite guts (Ohkuma, 2003), may be a source of novel microorganisms with wide-ranging industrial applications.

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