Diversity, diversity indices and tropical cockroaches.

The diversity of samples of cockroaches (Blattaria) taken with light-traps in six localities in Panama is described. As a diversity index α of the log series is found to be more satisfactory than either N 2 or N 1 of Hills's series or Hurlbert's S m, even if the distribution of the relative abundances is significantly different from a log series. However, even the α-index is of only limited usefulness. A simple statistic such as the number of species per unit effort can be at least as useful. The seasonal variation in the value of the diversity indices is negatively correlated with both the number of species and the number of individuals. Mountain sites have a lower alpha-diversity than lowland sites and relatively undisturbed sites have more individuals and more species than disturbed ones, although this difference is not reflected in the value of the diversity indices. To describe the beta-diversity the NESS similarity index, here called C m, is far superior over any other indices available. The between site diversity is very high. Samples taken at the same site in successive years in most cases are significantly different from being random samples of the same fauna.