1976] Waddington — Foraging Patterns of Halictid Bees 
117 
of mean bee density (Y = 0.214 + 0.006 X; the slope is significantly 
different from zero; F - test, P < 0.001). 
The null hypothesis of random dispersion of the halictids was 
rejected (chi-square test; P < 0.05) for only two of the eleven fre- 
quency distributions (Table 1). In both cases, C.D. > 1. Also, 
analyses of individual species data taken on July 3 (quadrats 8-11) 
show no association of individuals of the three possible species 
pairs (G - test on 2 X 2 tables; P > 0.05 for each comparison). 
The data indicate that the halictid species are primarily foraging 
at bindweed independently of one another; however, it is possible 
that the bees may also exhibit clumped dispersal patterns indicating 
a multiple halictid species group foraging strategy. 
Samples of the three halictid species at quadrats 8-1 1 were ob- 
tained to determine the temporal patterns of individual halictid 
species. All twelve frequency distributions (4 distributions for 
each species) were not significantly different (chi-square test; 
P > 0.05) from the expected Poisson distributions. The bees appear 
to forage independently of conspecifics. 
Spatial patterns — The data obtained during three tests on July 5 
are not significantly different from the three respective expected 
frequency distributions. These data indicate, again, that the bees 
are distributed at random and foraging independently of each other. 
Discussion 
The temporal and spatial data indicate that Agapostemon 
texanus, Augochlorella striata, and Lasioglossum ( Dialictus ) 
sp. forage at bindweed flowers as individuals, independently of 
one another. The bees appear not to forage in single or multiple 
species groups, nor are the patterns repulsed as might be expected 
for organisms utilizing the same resource in the same time and 
space. Bee numbers per area increased linearly with flower den- 
sity (Fig. 2) indicating that even at the highest bee densities en- 
countered in this study the threshold distances between individuals 
were not met (Ricklefs, 1973). If bee density were increased, the 
threshold of bees’ individual distance would be reached, perhaps 
resulting in repulsed spatial and temporal patterns. 
The possibility still remains that species associations occur 
among the bees, and that the spatial and temporal patterns are 
other than random. This is because the results obtained using 
