1987] 
Tietjen, Ay y agar i, & Uetz — Social spiders 
155 
Table 1. Relative growth (average of triplicates) and odor of microflora on dif- 
ferential media. Determination of colony type was based on colony morphology and 
growth was scored within individual plates (“+” indicates relative number of colonies; 
no colony growth and/or no odor; “S” a sweet odor, similar to that of the Mallos 
gregalis nest; “R” a rancid odor; and “nt” indicates not tested). 
SOURCE SABORAUD 
Yeast 
Mold 
Bacteria 
Odor 
Flies fed upon by M. gregalis 
+ 
+ 
- 
S 
Non-fed-upon flies 
+ 
++ 
+ 
R 
Female M. gregalis 
- 
+++ 
++ 
R 
Clean silk from M. gregalis nests 
- 
++ 
+ 
R 
Fly food (unsoiled) 
- 
++ 
+ 
R 
Fly food (soiled from fly cage) 
- 
+++ 
++ 
R 
Flies fed upon by other species 
- 
+++ 
++ 
R 
of spiders 
SOURCE 
Flies fed upon by M. gregalis 
+++ 
+ 
PYG 
S 
Non-fed-upon flies 
++ 
++ 
- 
S 
Female M. gregalis 
- 
+++ 
++ 
R 
Clean silk from M. gregalis nests 
- 
++ 
+ 
R 
Fly food (unsoiled) 
- 
++ 
+ 
R 
Fly food (soiled from fly cage) 
- 
+++ 
+ 
R 
Flies fed upon by other species 
nt 
nt 
nt 
nt 
of spiders 
SOURCE 
Flies fed upon by M. gregalis 
+++ 
+ 
TSA 
+ 
S 
Non-fed-upon flies 
+ 
+ 
+++ 
R 
Female M. gregalis 
nt 
nt 
nt 
nt 
Clean silk from M. gregalis nests 
nt 
nt 
nt 
nt 
Fly food (unsoiled) 
nt 
nt 
nt 
nt 
Fly food (soiled from fly cage) 
nt 
nt 
nt 
nt 
Flies fed upon by other species 
nt 
nt 
nt 
nt 
of spiders 
Non-fed-upon flies cultured on TSA agar had a rancid odor due 
to the large number of bacterial and non-yeast fungal colonies. 
However, non-fed-upon fly homogenates on differential media 
(PYG and Saboraud) indicate that the yeasts are normally present 
on the flies before feeding by M. gregalis. Other potential sources of 
microbiota (fly food, adult female M. gregalis, and silk) did not 
contain the yeasts. 
