9.5.1. Fungivorous insects

Fungi and, to a lesser extent, slime molds are eaten by many insects, termed fungivores or mycophages, which belong to a range of orders. Amongst insects that use fungal resources, Collembola and larval and adult Coleoptera and Diptera are numerous. Two feeding strategies can be identified: microphages gather small particles such as spores and hyphal fragments (see Plate 3.7, facing here) or use more liquid media; whereas macrophages use the fungal material of fruiting bodies, which must be torn apart with strong mandibles. The relationship between fungivores and the specificity of their fungus feeding varies. Insects that develop as larvae in the fruiting bodies of large fungi are often obligate fungivores, and may even be restricted to a narrow range of fungi; whereas insects that enter such fungi late in development or during actual decomposition of the fungus are more likely to be saprophagous or generalists than specialist mycophages. Longer-lasting macrofungi such as the pored mushrooms, Polyporaceae, have a higher proportion of mono- or oligophagous associates than ephemeral and patchily distributed mushrooms such as the gilled mushrooms (Agaricales).

Smaller and more cryptic fungal food resources also are used by insects, but the associations tend to be less well studied. Yeasts are naturally abundant on live and fallen fruits and leaves, and fructivores (fruit-eaters) such as larvae of certain nitidulid beetles and drosophilid fruit flies are known to seek and eat yeasts. Apparently, fungivorous drosophilids that live in decomposing fruiting bodies of fungi also use yeasts, and specialization on particular fungi may reflect variations in preferences for particular yeasts. The fungal component of lichens is probably used by grazing larval lepidopterans and adult plecopterans.

Amongst the Diptera that utilize fungal fruiting bodies, the Mycetophilidae (fungus gnats) are diverse and speciose, and many appear to have oligophagous relationships with fungi from amongst a wide range used by the family. The use by insects of subterranean fungal bodies in the form of mycorrhizae and hyphae within the soil is poorly known. The phylogenetic relationships of the Sciaridae (Diptera) to the mycetophilid “fungus gnats” and evidence from commercial mushroom farms all suggest that sciarid larvae normally eat fungal mycelia. Other dipteran larvae, such as certain phorids and cecidomyiids, feed on commercial mushroom mycelia and associated microorganisms, and may also use this resource in nature.

Chapter 9