1974] Evans, Matthews & Callan — Rubrica surinamensis 339 
often forming a rather flat, fan-shaped area as much as 16 cm wide 
and extending as much as 14 cm from the entrance. The pounding 
movements, made with the tip of the abdomen when making the pile 
and at each nest closure, were sometimes audible up to 3 m away. 
The entrance piles were used as periodic perches to which the females 
returned off and on throughout the day. We rarely observed aggres- 
sion between females on adjacent piles, and we do not regard them 
as territorial perches. 
Many details of this behavior were confirmed in Argentina, but 
some differences were noted. At Yacochuya, leveling of the mound 
seemed not to occur, the wasps merely scraping soil from the im- 
mediate vicinity of the hole when making the pile over the entrance. 
Thus each nest came to be marked by a small pile surrounded by a 
smooth area 2-4 cm across, and finally, on one side, the remains of 
the mound, usually 7-8 cm wide X 10-13 cm long X 1-2 cm deep. 
We noticed several nests here that had short grooves or “back bur- 
rows” into the mound, only 1-2 cm deep. These were made at the 
time of temporary or final closures, and appeared to represent quar- 
ries for obtaining soil for fill. One nest at Las Termas, still active 
and containing a half-grown larva, had a well-defined accessory bur- 
row 4 cm long, about 1.5 cm from the true burrow and at a right 
angle to it. 
Nest Structure 
The nest is a simple, oblique burrow with a terminal cell. All who 
have worked on this species have found the burrow to be very short 
(summary in Evans, 1966). Our studies confirmed this. One nest 
at St. Augustine had a burrow about 15 cm long ending in a cell 
about 3.5 cm long. Burrows at Cali averaged even shorter than this, 
although burrows at all three localities in Argentina were somewhat 
longer (Table 1). We attribute this to the fact that the soil at the 
Cali site was unusually hard. We found that cells when first made 
measured about 15 mm in diameter by 25-30 mm in length, but as 
the larva grew tended to be lengthened to as much as 4 cm. 
In contrast to previously published observations, we found that 
nests were often multicellular. That is, after completing the pro- 
visioning of the initial cell, the female often made another cell from 
a short side-burrow of the same nest. Of the 22 nests excavated at 
Cali, 8 had one cell, 8 had two, 5 had three, and 1 appeared to have 
five (but we are not certain that all five belonged with this nest). 
The cells of any one nest were at about the same depth and were 
