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Psyche 
[Vol. 94 
Fig. 1. a. Interior of Mallos colony, showing fly carcasses; b. SEM photo of 
microbiota community found on the interior abdomen of a fly from a Mallos 
colony; c. SEM photo of yeasts; d. SEM photos of individual collapsed yeast cells. 
Results 
If spiders are not fed while building their nests in the laboratory, 
the webs do not acquire the sweet odor until prey ( Musca domes- 
tica) are provided. Removal of fly carcasses is associated with a loss 
of this odor, suggesting that microbiota associated with the flies or 
feeding process of the spiders might be responsible for the scent of 
Mallos nests. Microscopic examination of fly carcasses reveals the 
presence of numerous hyphae, sporulating bodies, and budding 
yeasts (Fig 1). 
Flies that had been killed and fed upon by M. gregalis had an 
altered microbiota when compared to most of the controls (Table 1). 
The odor of the yeast cultures (PYG plates) was very similar to that 
of healthy M. gregalis nests, and subculturing suggested the pres- 
ence of three morphologically-distinct types of yeasts. 
