Beetles and fungi are a very interesting and diverse subject. For many species of Coleoptera fungi are the only source of food. Some beetles spend their entire life cycle from egg to adult inside fungi. For others surface of fungi is the most common substratum. There are groups of beetles that specially grow fungi "plantations" for feeding their larvae. Eventually, unicellular fungi act as vitally important endosymbionts of beetles: developing in stomach or intestine they participate in food processing. The role of fungi in life of beetles is reflected even in the Russian names: hairy fungus beetles, pleasing fungus beetles, handsome fungus beetles, minute tree fungus beetles, minute fungus beetles.
Relationships of fungi and beetles are very diverse, sometimes acquiring quite complicated form. Beetles feeding on non-living organic matter feed on fungi or use symbiotic fungi for its decomposition. Representatives of more than 100 families of beetles are to a certain extent related to fungi, and some are associated with them exceptionally. Inhabitants of fungi and substrata with fungal components are mostly mycetophages in the broad sense, and some of them are predators, i.e. Carabidae, Histeridae, Synteliidae, Trogossitidae, Cleridae, Melyridae, etc. The division of insects into myceto- (or myco-) and sapro- (detrito- or schiso-) phages cannot be quite distinct, because practically in many cases it is difficult to establish whether feeding on fungi proper or on their vital activity products takes place. On the other hand, when beetles do not feed on fruit bodies or plasmodium of Myxomycota it is very difficult to establish the fact of pure fungus-eating because also different protozoans and saprogenic bacteria participate in the processes of organic matter decomposition. Eventually, some species of fungi became facultative or obligatory symbionts of beetles supplying them with enzymes that are not produced by the digestive system of insects; other fungal species turned into parasites sometimes being quite aggressive pathogens. Some species acquired an opportunity to develop in mycetelial and ambrosial forms (the latter is formed in symbiosis with insects).
In this part the term mycetophagy (or mycophagy) is used in the broad sense including also sapro- and detritophagy, although not infrequently mycetophagy is only understood as feeding on fungi and Myxomycota (Kirejtshuk, 1989). Sometimes also macromyceto- and micromycetophagy are distinguished, the former term is used in case of feeding on large fungal particles and the second for feeding on small scattered fungal particles. Moreover, not infrequently a specific regime of feeding is observed, sporophagy, when both sexual spores and conidia (asexual spores) are predominant in the diet. And, eventually, among mycetophages there is a group, sucking fungi content, termed mycetoresorptors (the term is proposed for the first time) without external digestion (e.g. some Cerylonidae) or after injection (e.g. some Oxyporinae of Staphylinidae). Beetles characteristic of bark and wood affected by ambrosia may be called ambrosia-phages (the term is proposed for the first time). Apart from that, beetles inhabiting environment poor in proteins (such as wood) compensate for the deficit in the diet consuming dead animals and even by active predation.
It is worthy of note that all or apparently the majority of fungivorous beetles and also beetles consuming dead wood are characterized by intestinal symbionts belonging to yeast fungi or yeast-like fungi of Ascomycota. Such symbionts have already been found among mycetophages of the superfamilies Staphylinoidea, Eucinetoidea, Scarabaeoidea, Dryopoidea, Dermestoidea, Bostrichoidea, Cleroidea, Cucujoidea, Tenebrionoidea, Chrysomeloidea (Cerambycidae), Curculionoidea (Anthribidae, Cryptorhynchinae, Scolytinae, Platypodinae) whereas all the studied predators and phytophagous forms do not have fungal symbionts.
An important aspect of relations of beetles and fungi are devices of the former favouring dispersal of the latter. Very frequently spores, conidia and particles of mycelium are transferred by beetles on the body surface in comparatively deep punctures. However, not infrequently additional large external impressions develop - mycangia and mycetangia that become specialized containers for transferred fungal particles. Eventually, some beetles transfer fungi in specialized internal organs - mycetomes, which are normally arranged along the intestine with its outlet into the lumen or at the base of the ovipositor with outlet into the lumen of female excretory ducts. It has been discovered that in the organism of female of some beetles egg is infected by internal symbionts (this concerns bacterial rather than fungal symbionts).
Mycetophagous beetles occur in all habitats although they are most abundant, in fruit bodies of fungi and plasmodium, or at least in places of concentration of decomposing organic matter, primarily in subcortical spaces, decaying wood, leaf litter, dead animals, etc. Lawrence and Milner (Lawrence & Milner, 1996) distinguish the following types of fungal substrata used by insects:
Relations between beetles and fungi and also structural co-adaptations of both groups of organisms to each other are reflected in many publications, particularly numerous in the area of forest entomology. Relatively detailed reviews of these relations and structural characteristics can be found in works by Benik (1952), Crowson (1981, 1984, see list applied to the personal page), Lawrence and co-authors (Lawrence, 1989; Lawrence & Milner, 1996; Lawrence and Newton, 1980, see list applied to the personal page) and others. In the recent Russian literature they are discussed in detail mostly for beetles related to wood fungi. We should mention in the first turn works by A.V. Kompantsev (see the list applied to the personal page), T.V. Kompantseva (see the list applied to the personal page), G. O. Krivolutskaya (see the list applied to the personal page), B.M. Mamayev (1977), M.Yu. Mandelshtam (see the list applied to the personal page), N.B. Nikitsky (see the list applied to the personal page), V.A. Pototskaya (1976, 1978, 1982, etc.), V.M. Yanovsky (see the list applied to the personal page). Studies on physiology and biochemical processes of digestion of fungivorous beetles have been considered in many works (Sokoloff, 1972-1977; Martin, 1979, 1987, 1991; Martin et al, 1981, etc.), particularly in the most recent works on bark-eating beetles and works dealing with physiology of sap beetles having become laboratory objects for study, such as species of the genus Carpophilus beginning from the excellent publications of G.O. Stride (1953), Buchner (1953) and (Francke-Grosmann, 1967, 1975) up to numerous papers of the past decade (De Guzman et al., 1994; Brandhorst et al., 1996, etc.). It has been established relatively recently that some mycetophages are also capable of extraenteric digestion as well as predators (Leschen & Allen, 1988). On the Internet there are many pages on relations of beetles and fungi and also extensive bibliography on these issues.
We have also original information, i.e. data given to us by Yu.K. Novozhilov. He promised a long time ago to write for our site a survey of relations of beetles and myxomycets. So far he has given to the editors an abstract of a paper reviewed by him to be published in the journal "Mycology and Phytopathology". The paper is devoted to beetles found on myxomycets in Oka Reserve.
A.G. Kireitshuk, June 2002
Мамаев, Б.М. 1977. Биология насекомых-разрушителей древесины. В: Итоги науки и техники. Энтомология. Москва, 1-214.
Потоцкая В.А. 1976. Личинки жуков-стафилинид (Coleoptera, Staphylinidae), развивающихся в древесине. В сб.: Эволюционная морфология личинок насекомых. Москва, Наука, 156-174.
Потоцкая В.А. 1978. Морфология и экология личинок некоторых жуков-блестянок рода Epuraea Er. (Coleoptera, Nitidulidae). Энтомологическое обозрение, 57, 3: 570-577.
Потоцкая В.А. Морфо-экологические типы личинок Staphylinoidea (Coleoptera). Морфо-экологические адаптации насекомых в сообществах. Москва, Наука, 37-58.
Brandhorst, T., Dowd, P.F. & Kenealy, W.R. 1996. The ribosome-inactivating protein restrictocin deters insect feeding on Aspergillus restrictus. Microbiology, 142: 1551-1556.
Buchner, P. 1953. Endosymbiose der Tiere mit pflanzenlichen Mikroorganismen. Birkhauser, Basel.
Crowson R.A. An Ecological Triangle: Beetles, Fungi and Trees. // In: The Biology of the Coleoptera. London: Academic Press, 1981. P. 559-583.
De Guzman, F.S., Bruss, D.R., Rippentrop, J.M., Gloer J.B., Wicklow D.T. & Down P.F. 1994 Ochrindoles A-D: New bis-indolyl benzenoids from sclerotia of Aspergillua ochraceus NRRL 3519. Journal of Natural Products 57: 634-639.
Franke-Grosmann H. 1967. Ectosymbiosis in wood-inhabiting insects. In: Henry S.M. (ed.) Symbiosis. Vol. 2. Academic Press, London & New York, 141-205.
Franke-Grosmann H. 1975. Zur epizoischen und endozoischen Uebertragung der symbiotischen Piltze des Ambrosiakaefer Xyleborus saxenesi (Coleoptera, Scolytidae). Entomol. German. 1, 3-4: 279-292.
Leschen, R.A.B. & Allen, R.T. 1988. Immature stages, life histories and feeding mechanisms of three Oxyporus spp. (Coleoptera: Staphylinidae: Oxyporinae). Coleopterist's Bulletin, 42: 321-327.
Martin, M.M. 1979. Biochemical amplications of insct mycophagy. Biological Review, 54: 1-21.
Martin, M.M. 1987. Invertebrate-microbial interactions: ingested fungal enzymes in arthropod biology. Cornell University Press, Ithaca, New York.
Martin, M. M. 1991. The evolution of cellulose digestion in insects. Philosophical Transactions of the Royal Society of London. B 333: 281-288.
Martin, M.M., Kukor, J.J., Martin J.S., O'Toole, T.E. & Johnson, M.W. 1981. Digestive enzymes of fungus-feeding beetles. Physiological Zoology, 54: 137-145.
Sokoloff, 1972, 1975, 1977. Biology of Tribolium. Vol. 1, Vol. 2, Vol. 3. Oxford University Press, London.
Stride, G.O. 1953. On the nutrition of Carpophilus hemipterus L. Transactions of the Royal Entomological Society of London, 104: 171-194.