1974 ] Evans j Matthews t & Callan — Rubrica surinamensis 335 
raphy, to substrate, or to population density, the following synthesis 
of our notes from these various localities may serve to clarify this 
relationship. We also include a description of the larva and of the 
cocoon, in the hope of shedding light on the relationship of Rubrica 
to other genera of Bembicini. 
Distribution and Ecology 
R. surinamensis ranges from Trinidad and southern Mexico to 
central Argentina, being absent only from forested areas, higher 
mountains, and the friable sand of dunes and beaches. Because of its 
propensity for nesting in roads and paths, often in populated areas, 
it is one of the most commonly observed of solitary wasps, and its 
large size (17-24 mm) and pattern of yellow maculations against a 
rufous and fuscous background render it especially likely to attract 
attention. Since this species is subject to much variation in color, 
it should be pointed out that the populations we studied were all 
“typical of the species”, that is, without discal yellow markings on 
the mesocutum or other unusual features. We found no consistent 
differences in color or structure between Argentinian wasps and 
those from northern South America, despite behavioral differences 
to be pointed out below. 
As noted above, the aggregations at Cali, Colombia, and at St. 
Augustine, Trinidad, both occupied hard-packed roads. At Cali, an 
estimated 150 females nested along the road for a distance of about 
25 m, many nests being separated by 0.5- 1 m, but some clustered so 
that entrances were only 3-15 cm apart. The soil here is best de- 
scribed as clay-sand containing many small stones. At St. Augustine, 
the nesting aggregation varied seasonally from about a dozen to an 
estimated 50 individuals. These occupied an area of about 50 m 2 , 
with nest entrances 25 cm to 1 m or more apart. The wasps occu- 
pied the same site at least from 1941 to 1944. The aggregation at 
Cali is also known to have persisted at the same site for several years. 
On Trinidad, R. surinamensis has also been found nesting at the 
Erin Savanna, an area of open, virtually uninhabited country sur- 
rounded by evergreen seasonal forest, typical of the sandy soils of 
the south of the island. Here it nested in company with Stictia 
pantherina ( Handlirsch) . At other sites, R. surinamensis has been 
found nesting essentially alone, as few other bembicine wasps are 
adapted for digging in so hard a substrate. 
The three small aggregations near Tucuman, Argentina, were in 
diverse situations. At Yacochuya, 8 km northwest of Cafavate, Salta, 
