Cockroaches that excavate permanent burrows in solid materials such as wood or compacted soil are more specialized than those that use loose substrate or crevices. They typically exhibit a suite of ecological and behavioral features associated with their fossorial existence, and external morphology tends to converge. There are two major groups that fall into this category, the Cryptocercidae and the Panesthiinae, the latter of which includes the soil-burrowing cockroaches. There are other species whose morphology suggests they are strong burrowers, but little has been published on their field biology. The hissing cockroaches, including Gromphadorhina portentosa, have the general demeanor of burrowers. In a recently published book on the natural history of Madagascar, however, the only mention of these cockroaches is as prey for some vertebrates and as hosts for mites (Goodman and Benstead, 2003).
Burrows in solid substrates offer mechanical protection, as well as shelter from some classes of parasites and predators. The fact that dispersal in both the Cryptocer-cidae and Geoscapheini occurs following rainfall when excavation is likely to be more efficient (Rugg and Rose, 1991; Nalepa, 2005) suggests that burrow creation is energetically costly. Pathogens may accumulate in tunnels, and occupants may not be able to escape if a predator enters the excavated space. It is unknown if burrowing cockroaches have strategies for dealing with flooded burrows, or with the often peculiar O2 to CO2 ratios that may occur.
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