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[Vol. 88 
which occur buried in litter, inside rotting logs, or on roots deep 
underground where the opacity of the environment precludes 
attraction as a function of light. 
Among surface dwelling arthropods, there is no indication of a 
light-avoiding taxon. This does not preclude repulsion. A rare, but 
dangerous, enemy could keep fungal lights burning but escape 
inclusion in the present sample, especially since mycelia baited traps 
were not placed in the area of greatest mycelial abundance, deep in 
the leaf litter. The intended receiver may not be an arthropod or 
even macroscopic. Protozoa sometimes respond to lights. A glow 
could repel certain pathogens and keep the fungus free of particular 
diseases. 
Light as a warning signal: Lights emitted by unpalatable fungi 
might serve as warning signals directed towards nocturnal fungi- 
vores (a similar function has been hypothesized for ancestral 
flowers, Hinton 1973). Of North American fungi with luminous 
fruiting bodies, one, P. stypticus, is a bitter tasting purgative, while 
another, Omphalotus olearius, is a toxic hallucinogen (Miller 1979; 
the palatability of D. pusillus is unknown). Pleurotus japonicus, a 
luminescent Japanese species, is deadly poisonous (Buller 1924). 
However, the luminous fruiting bodies of Malaysian Mycena 
manipularis are quickly attacked by fungus gnats (Corner 1954; 
gnats could be specialists, immune to toxins). Again there is no 
evidence of arthropods avoiding fungal lights. My traps, of course, 
would fail to quantify the discouragement of deer or other large 
fungivores. 
Like aposematic insects, luminous mushrooms often occur in 
clumps (kin groups?) (see illustrations in Buller 1924, Harvey 1957; 
also descriptions in Wassink 1978). Aggregations might intensify 
warning signals (Cott 1957) and be instrumental in the evolution of 
conspicuousness (Fisher 1930, for arguments concerning the kin 
selection of aposematism). Several tropical light emitters, however, 
apparently occur singly (see Wassink 1978). 
White fungi can reflect enough celestial light to be surprisingly 
obvious at night (noticed at twilight by Lloyd 1977). An assumption 
of similar receivers for the bright white and luminous signals of 
fruiting bodies allows the nocturnal aposematic signal hypothesis to 
be tested with a larger sample. Mushrooms that appear to me to be 
uniformly bright white include 6 toxic species, 13 edible and 5 whose 
