  Applying the microcanonical definition of entropy to a weakly interacting and
self--gravitating neutralino gas, we evaluate the change in the local entropy
per particle of this gas between the freeze out era and present day virialized
halo structures. An ``entropy consistency'' criterion emerges by comparing
theoretical and empirical estimates of this entropy. We apply this criterion to
the cases when neutralinos are mostly B-inos and mostly Higgsinos, in
conjunction with the usual ``abundance'' criterion requiring that present
neutralino relic density complies with $0.2<\Omega_{{\tilde\chi^1_0}} < 0.4$
for $h\simeq 0.65$. The joint application of both criteria reveals that a much
better fitting occurs for the B-ino than for the Higgsino channels, so that the
former seems to be a favored channel along the mass range of $155 \hbox{GeV} <
m_{{\tilde\chi^1_0}} < 230 \hbox{GeV}$. These results are consistent with
neutralino annihilation patterns that emerge from recent theoretical analysis
on cosmic ray positron excess data reported by the HEAT collaboration. The
suggested methodology can be applied to test other annihilation channels of the
neutralino, as well as other particle candidates of thermal WIMP gas relics.
