How to use interactive keys

The umbrella key (Crustacea, the Higher Taxa) identifies the higher taxa of the world Crustacea and leads into the keys to the crustacean families. There are 56 higher taxa (an arbitrary assignment which basically divides the crustaceans into familiar or natural groupings). Some of these are familiar, such as the brachyurans (crabs), the carideans (shrimps), the anostracans (fairy shrimps) and euphausiaceans (krill), and some are obscure, such as the monstrilloids (parasitic copepods) or mictaceans.

Once you know which group you have, then select the family or family/generic level key to that group. The first step is to accurately identify the higher taxon.

Interactive keys differ from traditional dichotomous keys in that you can select any available character for the identification and you can re-identify your taxon more than once using different sets of characters. As you make character state selections taxa are eliminated and the remaining taxa are listed on the screen until only one or none are left.

In interactive keys there are several kinds of characters:

1. Multistate characters are the most common and useful.
2. Integer characters define numbers, such as the number of articles in an antenna or the number of pairs of legs.
3. Real number characters, such as the ratio of the length of antenna 1 to antenna 2.
4. Text characters, such as synonymies, geographical distributions or remarks. These characters are used for information retrieval about an identified taxon.