1974] Evans , Matthews £sf Callan — Rubrica surinamensis 337 
using the mandibles to cut through the soil and to haul out small 
stones, the front legs to scrape loosened soil beneath the body 
(Fig. 1). Apparently the better part of one day is required for 
completion of a nest. When the burrow and cell are complete, the 
female partially disperses the mound of soil and constructs a rounded 
pile of soil over the entrance. This pile serves as a perch to which 
she returns intermittently as long as the nest is active (Fig. 3). 
Since this “pile-building” behavior is, so far as we know, unique, 
we present in some detail our notes on a typical individual at Cali 
(RWM, note C6). 
This female was observed digging steadily from 1030 to 1100 
hours on 11 January 1972. She then came out, made a closure, and 
flew off, leaving the accumulated soil intact. She returned more 
than an hour later, opened the nest, and resumed digging. She spent 
much time in the burrow, from time to time emerging and scraping 
soil onto the mound, then re-entering to dig further. At 1358 she 
came out, closed the entrance, and walked slowly to the end of the 
mound, where she turned in a circle several times while scraping 
sand in all directions. After spending 3 minutes leveling in this 
manner she flew off, returning 5 minutes later with a small fly. In 
25 seconds she emerged from the nest, turned around outside and 
immediately re-entered, remained inside 35 seconds, then came out 
again. This sequence of going in and coming out was repeated 1 1 
times. (Several other females were seen to exhibit similar behavior, 
which we assume to play a role in familiarizing the wasp with the 
new nest.) 
Following this the female made a strong outer closure, packing the 
soil with vigorous blows of the tip of the abdomen, and then resumed 
leveling. She did this by walking to the end of the mound while 
scraping soil back toward the entrance, then turning around and 
walking to the entrance without scraping; then turning around again 
and walking to the end of the mound scraping soil. This was re- 
peated many times over a 12-minute period, the result being removal 
of most of the soil to a heap over the entrance. The wasp dragged 
several pebbles onto this pile and periodically tamped it with the tip 
of her abdomen. Eventually she made several short flights ; each time 
she returned adding a little more soil to the pile, which now meas- 
ured 35 mm X 25 mm X 7 mm deep in the center. 
We observed similar behavior on many occasions at Cali. Often 
the pile was surrounded by a ring of smooth soil, where the loose 
surface soil had been scraped upon it. The original mound, resulting 
from the digging of the nest, was sometimes partially in evidence, 
