Cockroaches in this category either tunnel in uncom-pacted substrate (loose soil, dust, sand, guano), which may collapse around them as they travel through it, or they utilize small, preexisting spaces (dirt clods, leaf litter, and other plant debris), which their activities may enlarge. Many remain beneath the surface only during inactive periods, although those in guano and leaf litter, particularly juveniles, may conduct all activities there. Certainly the largest class in this category are cockroaches that tunnel in plant litter found on forest floors, in the suspended soils of the canopy (e.g., in epiphytes, tree-holes, tree forks), and in piles concentrated by the actions of wind, water, or humans. Some species tunnel only as a defense from predators, or in response to local or seasonal conditions. Substrate categories are often fluid. Those that burrow in guano may also burrow in dirt, and those that tunnel in leaf litter may continue into the superficial layers of soil. Adults of Therea petiveriana in the dry, scrub jungles of India burrow in soil, leaf litter, and debris (including garbage dumps) during their non-active period (Livingstone and Ramani, 1978). The nymphs are subterranean and prefer the zone between the litter and the underlying humus, but may descend 30 cm during dry periods (Bhoopathy, 1997). Other versatile burrowers include Blaberus spp., which readily bury themselves in dirt or loose guano (Blatchley, 1920; Crawford and Cloudsley-Thompson, 1971), and Pycnoscelus spp., found in a wide variety of habitats as long as they can locate appropriate substrate for burrowing (Roth, 1998b; Boyer and Rivault, 2003). All stages of Pyc. surinamensis tunnel in loose soil, and are also reported from rodent burrows (Atkinson et al., 1991). The sand-swimming desert cockroaches fall into this category, as well as species such as Ergaula capensis, where females and nymphs burrow into well-rotted coconut stumps (Princis and Kevan, 1955), as well as the dry dust at the bottom of tree cavities (Grand-colas, 1997b). Blattella asahinai is known to burrow into leaf litter and loose soil; they are sometimes pulled up along with turnips in home gardens (Koehler and Patterson, 1987). Individuals of Heterogamodes sp. are known to bury themselves in sand or earth (Kevan, 1962). Several Australian species (Calolampra spp., Molytria veg-randa) seem to spend the daylight hours underground, emerging to feed after dark (Rentz, 1996; D. Rentz, in Roth, 1999b). When collected during their active period or in light traps they usually sport sand grains on their bodies. In caves, Eu. posticus nymphs burrow in the surface of loose guano. They may be completely concealed, or may rest with their heads on the surface with their antennae extended up into the air. If the guano is compacted, the cockroaches remain on its surface and are attracted to irregularities such as the edge of a wall, a rock, or a footprint (Darlington, 1970). The recently described species Simandoa conserfariam congregates in groups of 20 to 50 individuals of all ages deep within the guano of fruit bats; none have been observed on the surface (Roth and Naskrecki, 2003).
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