Suppose r different animal species are found in some or all of c different habitats. Observations on the numbers of occurrences of the animals in the habitats can be tabulated in an r ° c table. The overall "diversity" of the table, HT say, is defined as Brillouin's information measure with the r ° c table's cell frequencies of the different "symbols." It is shown that HT may be split into two components in two different ways. The first way splits HT into HA, the diversity of the animal species, plus the weight mean of the within—species habitat diversities. The second way splits HT into HB, the diversity of the habitats, plus the weighted mean of the within—habitat species diversities. The weighted mean of within—species habitat diversities constitutes a measure of the average niche width of the r species of animals. The weighted mean of within—habitat species diversities constitutes a measure of the average niche overlap among the c habitats examined. The measures are of actual, realized niche widths and niche overlaps and are therefore inevitably affected by the relative abundances of the species and the habitats. A method of standardizing them is proposed. An example is given using data on the occurrences of several species of aphids on several host plants of the genus Solidago (goldenrods).