1970] Matthews & Evans — Sericophorus 415 
a large colony nesting on the lower slopes of Black Mountain, 
Canberra, A. C. T., behind the C. S. I. R. O. Entomology biddings. 
The soil containing nests was a sandy loam of rather firm and uni- 
form consistency forming a layer from 15 to 40 cm deep overlying 
coarse gravel and small rocks. Possibly these areas were parts of 
former stream channels on the mountain, since a few meters away 
the soil graded rather abruptly into loamy to hard clay, which 
characterized most of the lower slopes of Black Mountain. 
This wasp was extremely successful in this area and active nests 
were found from mid-December through April. Nests were con- 
centrated in three more or less contiguous areas. On 13 February 
1970, the largest of these nesting aggregations contained 88 active 
nests, concentrated in an area of about 8X2 meters along the 
fence bordering the Botanical Gardens. This area had been har- 
rowed for a fire break earlier in the summer and lacked vegetational 
cover. The smaller aggregations were estimated to contain 40-50 
active nests, and were in adjacent areas having a sparse herbaceous 
cover. Inter-nest distances were variable, but on several occasions 
active nests were noted within 5 cm of one another. 
Nesting Behavior. — Nineteen nests were excavated by the authors 
between 6 January and 18 April, 1970 (note numbers A 193, A 221, 
A 251, A 252, A 259-261, A 306, AM 141-144, AM 153, AM 
217). Representative nests are illustrated in Figures 1 and 2. 
Females dig a more or less vertical main shaft from 10-50 cm deep 
(ave. 21.3 cm), and construct up to 23 cells (ave. 5.6) at depths 
of 10-50 cm. Cells are placed in a radiating pattern, each at the 
end of a more or less horizontal lateral burrow extending 1-14 cm 
(ave. 7.0 cm) from the main tunnel. Cells are elliptical and more 
or less horizontal, measuring about 9 X 18 mm. The lateral 
tunnels leading to the cells are approximately perpendicular to the 
main shaft or inclined slightly upwards. A single cell is excavated 
at the end of each lateral tunnel, and after provisioning and ovi- 
position, the tunnel is completely refilled. In some nests (e.g., note 
AM 144) the first made or oldest cells were apparently deepest 
and more recent cells closest to the surface. However, in one 
7-celled nest the freshest flies and eggs were in the deepest cells 
(A 260), and in some nests the newer cells appeared to be inter- 
spersed at various depths between older cells (e.g., A 261). 
Nests are made conspicuous by the accumulation of a prominent 
rim-like mound, 6-8 cm across and O.5-2.O cm deep, surrounding the 
7-8 mm diameter entrances (Fig. 9). These buff-colored mounds 
contrasted strikingly with the grayish soil surface, and were easily 
