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Psyche 
[Vol. 88 
Discussion 
Attraction of insects to fungal lights does not demonstrate that 
luring arthropods is the function of the bioluminescence. With this 
caveat in mind, note that an acceleration in the rate of certain 
fungus /insect interactions even as an effect of a bioluminescent 
signal is apt to influence the evolution of luminous fungi. In 
particular, the argument that fungal lights are functionless, and by 
implication harmless by-products of metabolism, loses force (see 
also Lloyd 1977). Bearing a light near arthropods is unlikely to be 
selectively neutral (for counterviews, see Buller 1924; Prosser and 
Brown 1961). 
Some possible functions of fungal glows become more plausible 
with, or fail to find support in, the presented data. Both are 
discussed below. 2 
Attraction of spore dispersers: Stinkhorn fungi (Phallales) use 
odor, and perhaps color, to attract spore dispersing insects. Diptera, 
in particular, consume a sweet malodorous spore-containing mu- 
cous smeared on the fungal surface. Spores develop after being 
discharged in the insect feces (discussed in Ramsbottom 1953). An 
early conjecture on the function of fruiting body luminescence was 
that lights, like odor and color in stinkhorns, lure spore dispersers 
(Ewart 1906; see also Lloyd 1974, 1977). 3 
A large proportion of the animals attracted to luminous fungi are 
potential consumers of its spores. Many Collembola feed on fungal 
spores, mycelia, and fruiting bodies. Some members of captured 
Diptera families breed in fungi. The phorid Megaselia halterata, for 
instance, is a pest of cultivated mushrooms (Oldroyd 1964). Whether 
spores of D. pusillus pass unharmed through the insect gut is 
2 The following functions concern heterospecific receivers; however, biolumines- 
cence is often intimately associated with mating (see Lloyd 1977). Sexual congress in 
relevant Basidiomycetes consists of exchange of nuclei between haploid mycelia. Is it 
possible that glows might direct the growth of photo-sensitive hyphae at this stage 
and so serve as mating signals? Such an explanation fails to account for luminosity in 
diploid mycelia or the fruiting body. 
3 Insects may evolve an affinity for fungal lights due to “rewards,” in food, shelter, 
etc., the fungus provides. An alternative is that attraction is due to fungal 
exploitation of arthropod “phototropisms.” The function of “phototropisms” are 
often obscure. Some are apparently effects of orientation systems based on the 
relative position of celestial objects (see Lloyd 1977). 
