9. Ground-dwelling insects
A profile of a typical soil shows an upper layer of recently derived vegetational material, termed litter, overlying more decayed material that intergrades with humus-enriched organic soils. These organic materials lie above mineralized soil layers, which vary with local geology and climate, such as rainfall and temperature. Particle size and soil moisture are important influences on the microdistributions of subterranean organisms.
The decompositional habitat, comprising decaying wood, leaf litter, carrion, and dung, is an integral part of the soil system. The processes of decay of vegetation and animal matter and return of nutrients to the soil involve many organisms, notably fungi. Fungal hyphae and fruiting bodies provide a medium exploited by many insects, and all faunas associated with decompositional substrates include insects and other hexapods.
In this chapter we consider the ecology and taxonomic range of soil and decompositional faunas in relation to the differing macrohabitats of soil and decaying vegetation and humus, dead and decaying wood, dung, and carrion. We survey the importance of insect—fungal interactions and examine two intimate associations. A description of a specialized subterranean habitat (caves) is followed by a discussion of some uses of terrestrial hexapods in environmental monitoring. The chapter concludes with seven taxonomic boxes that deal with: non-insect hexapods (Collembola, Protura, and Diplura); primitively wingless bristletails and silverfish (Archaeognatha and Zygentoma); three small hemimetabolous orders, the Grylloblattodea, Embiidina, and Zoraptera; earwigs (Dermaptera); and cockroaches (Blattodea).