Certain organisms attract human interest without obvious economic benefits. This relationship should be of equal interest to ethnobiologists: ethnobiology is the scientific study of human perception of biota found in the surrounding landscape [1], the interaction between humans and other organisms, and the cultural expressions arising from this interaction. Folk biology may be defined as an understanding of the biological world: how human groups perceive, interpret and reason about living kind [2], and how they categorize, explain and understand biota in their environments at different points in time. Questions of how, when, where and for whom an organism has been important are crucial. Not only economically interesting species are of significance to humans; therefore, the entire surrounding biota should be studied [3] and it should be analysed not only in separate segments but also as an interconnected whole.

Why do taxa without any clear economic or practical use attract human attention? A keen interest in and curiosity about the environment can be observed especially in pre-industrial societies who depended on nature to a much higher degree than present-day urbanized and industrialized societies [4]. An important factor for interest is the unusual. Emotional associations can explain some ideas about plants: for instance, strong fears, needs or desires can be associated with an existing or occurring external, conspicuous or strange factor or element. Carl-Vilhelm von Sydow notes the importance of trees in the cognitive reality of pre-industrial peasants in Sweden [5]: an odd or otherwise spectacular tree was assigned a role in folk medicine rites (tandvärksträd ‘toothache tree’); another tree had a taboo attached to it or ‘permitted’ the passer-by to have an alcoholic drink (suptall ‘schnapps pine’, usually a solitary pine tree along the road) [6]. Similarly, small organisms with a peculiar appearance or behaviour could attract attention without providing any immediate benefits [7]. ‘The first’ or ‘last’ in various contexts, such as the first sighting of a certain flower in spring, are common in folk biology [5, 8]. Such first or last plants were often ascribed health-giving or divinatory properties for the forthcoming harvest, expected arrival of winter, etc. [9]. All organisms recognized and named by humans provide various kinds of cultural ecosystem services, non-material benefits humans obtain from ecosystems through spiritual enrichment, cognitive development, reflection, recreation and aesthetic experiences [10], as well as folk and religious beliefs and various understandings, explanations and interpretations about the surroundings.

Research in historical folk biology and folk knowledge provides not only information about economically important organisms, but also about less known past relationships with biota, practices and uses. These ‘invisible’ aspects are as important as the ‘visible’ or obvious and easily identifiable human-biota relations, and therefore should be studied both separately and together with organisms of obvious practical use. One such example is the naming and local knowledge and belief in the origins of myxomycetes, an irrelevant and economically useless organism for humans in pre-industrial Sweden and its neighbouring countries: in the context and with the methods of historical ethnobiological analysis, and by employing a qualitative method in which ethnographic description plays an essential role, we are able to uncover not only a wealth of folk knowledge, interpretations, beliefs and religious connotations, but also several layers of human relations towards biota, including motivations for the destruction of specific organisms [9].

Among the many organisms with multiple and multilayered significances in the folk biology of peasants in Sweden and neighbouring Nordic countries, Denmark, Norway and Finland, are a few plasmodial slime moulds, Myxomycetes (Syn. Myxogastria) [11]. They are indeed weird beings: myxomycetes have some features in common with fungi and others with animals. They are clearly distinguished from other organisms by their morphology and temporality and their brightly coloured slimy bodies, which rapidly change shape and size as they grow. They do not resemble animals, plants or fungi, yet they are easy to spot when they suddenly appear on decaying wood in the vicinity of human settlements. A slime mould can move across substrates like a large amoeba while consuming everything in its path, including bacteria, spores and other organic materials [12]. About 400 taxa, distributed over 57 genera, have been documented in these Nordic countries [13, 14]. SLU, the Swedish Species Information Centre (Artdatabanken, Species data bank), reports 239 taxa for Sweden [15]. Myxomycetes are usually found in dark and damp environments in the forest, where they grow on rotting trees and branches, bark, moss and decaying leaves. They can be observed either in the motile stage, so-called plasmodium, or as fruiting bodies. The slime coat protects the plasmodium from drying out and thus, when crawling, myxomycetes usually leave a trace of slime [16].

Scientific interest in these organisms dates back to the mid-seventeenth century: the German physician Thomas Panckow presented wolf’s milk in Herbarium Portatile in 1654; the first scientific description of Fuligo septica was given by the French botanist Jean Marchant in 1727, who called it fleur de tan ‘bark flower’ and classified it as a sponge [17]. Carl Linnaeus named the same taxon Mucor septicus in Species Plantarum (1763) [18]. The famous Swedish mycologist Elias Fries described numerous slime moulds as Myxogastres in 1829 [19].

The peasants in the Nordic countries commonly recognized three species among Myxomycetes: scrambled egg slime, Fuligo septica (L.) F.H.Wigg., wolf’s milk, Lycogala epidendron, (L.) Fr., and dog sick slime mould, Mucilago crustacea F.H.Wigg. All three were associated with folk beliefs until the late nineteenth century [20]. The peasants had no use for the slime moulds, yet these organisms played an important role in folk beliefs about witches and magic. In folk biology, slime moulds were connected with milk and butter, both important ingredients in the peasant diet; a witch who specially created a supernatural being for stealing these crucial ingredients; and the action of vomiting or spilling the stolen goods by the magical hare or cat while it was bringing the food back to the witch. Belief in the evil origins, with the devil at the root of it all (witches were supposed to contact directly with him), caused the peasants to destroy the organisms in various ways.

The earliest sources on trulsmör ‘troll/witch butter’ (Fuligo septica) in Sweden date to the sixteenth century; one source from September 1597 connects it with a witchcraft case [21]. (Fig. 1) A Norwegian source mentions trollkattsspyor ‘troll/witch-cat puke’ in 1658 [22]. Trulsmör is still known colloquially as trollsmör. In Swedish (including Finland-Swedish and Estonia-Swedish) and other Scandinavian languages (Danish, Norwegian), troll signifies both ‘troll’, a hairy, small-size forest being with a tail and limited magic capabilities, and ‘witch’, human, usually a woman. The verb trolla means ‘to bewitch, to use magic’. Other folk names of slime moulds are related to carrying, because the organisms were perceived as traces (vomit) of the supernatural being carrying stolen milk: bäreskarn’carrier filth’ is mentioned in a source from 1617, bjärsmör’carrier butter’ in a lexicon from 1630 and pukelort ‘small-devil dirt’ from 1672 [23]. The Swedish verb bära means ‘to carry’; bära, bjära for ‘[milk-hare/cat] carrier’ has in Finnish and the northern Meänkieli (Tornedalian Finnish) transformed to para. Globally, definitions of slime moulds as products of evil forces are very old: in a Chinese-language source from the fourth century, a substance that could be Fuligo septica was called gui shi ‘demon faeces’ [24].

© Ingvar Svanberg, 17 July 2024)

Fuligo septica can appear in different shapes, sizes and yellow nuances. Häverödal, Uppland province, central Sweden (Photo

This study discusses the folk biology related to slime moulds, a specific human-biota relationship, and the effects of folk beliefs on the organisms. Few ethnobiologists have taken more than a cursory interest in these organisms: Vagn J. Brøndegaard 1979 and N. Floro Andrés-Rodríguez & Oscar Requejo 2020 provide a broader comparative perspective from several countries [25, 26]. A brief review of Swedish data is presented by Ingvar Svanberg in 2005 [27]. María Mercedes Rodríguez-Palma et al. published in 2017 an interesting paper on myxomycetes used as food in Mexico, a practice unknown in the Nordic countries [28].