Numerically, arthropods certainly represent the major taxonomic group of hypogeal fauna. Moreover, as far as the range of their dimensions is concerned, arthropods that live in the soil detain a relevant record that is supported by the fact that their length extends from a few tens of µm of the most microscopic ticks to several tens of mm of the longer miriapods.
Generally speaking, the most relevant group of arthropods can be identified in the above-mentioned ticks, in collembola (wingless insects in the subclass Apterygota), in miriapods and in araneids. Considering the characteristics of the environments that are being studied, however, even other groups of arthropods can be significantly represented, such as pseudoscorpions, isopods (guinea pigs) and several winged insects such as coleopters, dipters and hymenopters.
On the premise that the arthropods resident in the soil cover a wide range, it is impossible to identify a dominant trophic characteristic that allows us to place them in a single ecological role. In other words, the arthropod fauna of the soil is so rich in both taxonomic and morphologic terms that the life styles and feeding habits of the different species practically cover the entire spectrum of the ecological niches that this environment offers. For example, among the arachnids, scorpions, opiliones and pseudoscorpions are all predators; however, many ticks and mites (also belonging to the class Aracnida) feed on decaying organic matter as isopods (crustaceans) do too. Among the miriapods there are numerous herbivores such as symphylans while the majority of chilopods and diplopods are respectively predators and eaters of detritus. If one goes on to investigate insects, the possibilities are almost infinite with groups such as the orthopterans
that are totally herbivorous and groups such as the diplurans that are mainly predators instead. Moreover, in between these two extremes, there is an intermediate group that comprises a vast series of arthropods whose diet is very variable. Suffice it to give the example of coleopters, to prove what a great diversity of feeding habits can exist within the same zoological group. The same can be said about hymenopters, hemipterans and dipterans.

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