What is the best method to identify different spider species?

The best method to identify different spider species among the provided options is examining their eyes. Spider species exhibit a wide variety of eye arrangements and structures, which can be critical distinguishing features for taxonomists and arachnologists. Some spiders have four pairs of eyes, while others may have fewer or even more, and their placement on the head can vary significantly from one species to another. These ocular characteristics are often genus- or family-specific, making them a reliable means of identification.

In contrast, while body color can provide some clues about a spider's identity, many species can exhibit a range of colors or patterns that change with age, environment, or even lighting. Counting legs is not a useful identification method since all spiders share the characteristic of having eight legs; therefore, this trait does not differentiate species. Measuring size can also be misleading, as size can vary widely within a species based on environmental factors, molts, and biological sex. Thus, examining eyes is regarded as the most consistent and informative method for identifying spider species.