1985] 
Porter — Masoncus in harvester ant colonies 
147 
I have collected Masoncus spiders from harvester ant nests in 
three widely separated areas south of Tallahassee, but they are 
probably much more widespread. Spiders were present in almost all 
of the harvester ant nests I excavated. Each nest contained from a 
few to several dozen spiders depending on the size of the colony and 
how carefully I excavated it. Females outnumbered males by four to 
one in my collections and were consistently the predominant sex. 
Spiders were distributed throughout the colony from the upper- 
most nest chambers to those more than two meters below the sur- 
face. Generally, They seem to prefer deeper (>60 cm) chambers with 
fewer ants, but I have also collected them from brood and seed 
storage chambers. On several occasions, I have even observed spi- 
ders briefly running out of the nest entrance. Spiders seem to prefer 
the ceilings and periphery of the nest chambers, perhaps because 
this reduces their contact with the ants. 
Spiders were present in the ant colonies throughout the year. 
Both adults and immatures have been collected in the months of 
March, May, June, July, August, September and November. These 
spiders have yet to be collected during mid-winter because cold 
weather severely inhibits my enthusiasm for excavating half frozen 
ant mounds. Very young spiderlings appear to be most common in 
the late months of summer. I have collected eggs in July and Sep- 
tember but may have overlooked them in other months as well. 
White egg sacks are laid in small depressions on the ceilings of 
nest chambers about one meter below the surface. The egg sack is 
3-5 mm across and contains 2-3 eggs (x = 2.6, n = 10). The exposed 
surface of the sack is very smooth and conforms evenly to the con- 
tour of the ceiling; if this were not so the ants might destroy the egg 
sack during chamber maintenance. Spiderlings emerge from the egg 
sacks after about three weeks (25° C) through a small hole cut in the 
surface just off center from the egg cluster. 
I am not certain whether these spiders are obligate or facultative 
guests, but the following evidence indicates that they are more than 
just casual residents of harvester ant nests: 1) I have never found 
them associated with other ants (e.g. Solenopsis, Trachymyrmex, 
Aphenogaster ) nor have I chanced across them living indepen- 
dently. 2) Most harvester ant colonies contain at least a few spiders. 
3) Spiders are found in harvester ant nests throughout the year. 4) I 
have observed spiders feeding in the nests. 5) All life stages are 
