26 
Psyche 
[March 
under surfaces of the Crysophila leaves, and were exclusively confined 
to these plants. This material is scraped from a roughly oval area 
approximately io cm in diameter, the nest being attached at the 
approximate center of the scraped area. (Fig. 5). While no ex- 
traneous foreign materials were incorporated in any M. comes nest, 
nests of M. myersi are reported to have earth pellets incorporated 
in the walls (Myers, 1934) and nests of M. hingstoni ( = guianen- 
sis) are said to have pellets of rotted wood included in the nest sac 
(Richards, 1932). By contrast, Howes (1925, 1933) states that 
nests of the latter species in British Guiana are made of moss and 
lichen fragments. 
The nest pedicel is loosely spiralled, usually with two coils, and 
when outstretched measures an average of 15 mm (range 12-18 mm). 
The single entrance, located at the nest apex beside the attachment 
of the pedicel, opens to one side (Fig. 4) ; in one case there was a 
double entrance opening to both sides. The nest sac is ovate or 
obconical; it averaged 17.4 mm long (range 12-26 mm) and 12.1 mm 
(range 8-15 mm) at its widest diameter. The outer surface varied 
in texture from relatively smooth to granulose. Only loosely bound 
together, the flocculent bottom half of the nest probably serves as 
a reservoir of material used for cell construction. In basic structure, 
M. theridii nests (Myers, 1934) are similar, measuring 12 mm 
long with a coiled pedicel of the same length. Photographs of sup- 
posed M. guianensis nests given by Howes (1933, repeated in Clark, 
1937) show a very short, uncoiled pedicel. However unless pedicel 
length is highly variable in the species, these nests are probably in- 
correctly ascribed. Rather, an earlier photograph of a nest with a 
very long, apparently uncoiled pedicel (Howes, 1925, p. 276) prob- 
ably represents the true M. guianensis nest, for this agrees closely 
with the nest of M. hingstoni recently placed in synonymy under 
M. guianensis (Krombein, 1967), having a pedicel measuring 60 mm 
(Richards, 1932). 
The upper half of the nest is hollow and covered internally with a 
smooth translucent coating, giving rigidity to the sac. The same 
material is found on the pedicel and lip of the entrance, and on the 
internal surfaces of the cells. The coating of the cells with a 
transparent substance seems to be unique in the Sphecidae but 
parallel cases are known in some bees (e.g. Colletidae). It is prob- 
able that the pedicel may be entirely secreted, for Myers (1934) 
noted that the reddish M. theridii nest sacs were held together by 
whitish silk-like strands which became thicker toward the nest apex 
