1965] 
Evans — A mmophila azteca 
13 
mandibles, often after “trying for size” several such lumps and 
rejecting each of them until one is found which fits the mouth of 
the burrow (Fig. 1). A small amount of sand is often scraped over 
this closure, but no pounding occurs. The wasp normally returns to 
this nest within a few hours or early the next day with the first prey, 
on which the egg is laid. The single nest studied at the Great Sand 
Dunes, Colorado, was like the many observed at Jackson Hole: the 
female removed a single small stone from the entrance before intro- 
ducing the first caterpillar and laying an egg upon it. 
Following oviposition, and after supplying each additional cater- 
pillar, a very different type of closure is made (Fig. 2). Again, 
various lumps and pebbles are “tried for size”, but this time the 
initial lump is placed well down in the burrow, at least half way 
down and often near the bottom; the object selected must lodge 
perfectly in the burrow so that material may be packed above it (this 
is the hauptverschlussklumpchen of Baerends and other European 
workers) . When the initial lump is in place, the wasp scrapes sand 
into the nest with her front legs, facing of course away from the hole. 
She may utilize some of the soil of the mound if this is close by ; or if 
loose soil is not available she may loosen some by biting the ground 
around the entrance. Periodically small pebbles or bits or earth are 
picked up and placed in the burrow with the mandibles. From time 
to time the wasp remains with her head down in the burrow and 
moves her body up and down, packing the soil in place with blows of 
the antero-ventral surface of the head in the usual manner of wasps 
of this genus. When the burrow is full, additional packing occurs, 
the wasp sometimes retaining her grasp on a small pebble while so 
doing (“using a tool”) and then leaving the pebble in place in the 
fill (Fig. 8). Finally, sand is scraped in various directions over the 
top, resulting in thorough concealment of the entrance. The closure 
is prepared very rapidly and requires only a minute or two; one wasp 
completed a typical temporary closure in only thirty seconds. It is 
probable that the same pebbles and lumps of earth serve in successive 
closures, so one would expect a reduction in the length of time re- 
quired after the first temporary closure. 
Final closure may be indistinguishable from temporary closure 
unless one follows the provisioning of the nest to determine that this 
is, in fact, the final closure. My limited data suggest that in the 
final closure ( 1 ) the initial lump is always placed at or near the 
bottom of the burrow (Fig. 3), and (2) packing with the head is 
relatively prolonged and some packing while holding a pebble in the 
mandibles always occurs toward the end of the closure (Fig. 8). 
