The keys consist of dichotomous blocks and matrix blocks. While it is clear how to move through the first, some details on how to use the latter, which might be less obvious, are discussed below. Information and some additional explanations are also included. Apart from trying to run a real specimen through a key with the intent to identify it, some sections provide an alternate way to move through the taxonomic hierarchy, finding images and basic information on diversity.
Entering the key
The key can be entered from the key entry page (accessible by clicking Key on the menu bar). It contains a list of entry points. When coming from the taxa display (Taxa in the menu bar), the key entry page lists one or more entry links to the current taxon if it is included in a key.
A large view of an image opens in a separate browser window after clicking on the thumbnail (pop-ups must be allowed for this website). To compare two or even more images in large view, the individual windows need to be adjusted in size and shifted appropriately on the screen — sometimes a bit cumbersome.
These blocks work like couplets in a classical printed key. But they are much more reliable when moving back to try different branches, in cases where the presented characters are ambiguous or when reaching a dead end. Although carefully developed, the keys reflect some of the imperfections of the source literature used for construction.
This type of block is truly interactive. It is possible to analyze characters in any order. It is also possible to reset the states of individual characters to “not specified” without resetting the whole block to its pristine condition. A matrix block not only can have three or more branches, but each character can have more than two states. In characters with numerous states (some of which might be very similar), it can be very useful to exlude one or more states rather than selecting one.
Links to taxon pages open in a separate browser tab. Before returning to proceed in the key, the second browser tab should be closed. Otherwise an error might occur due to conflicting session information. Should this happen, simply click on Key on the menu bar of the second browser tab containing the taxon page. One or more links into the key will be provided for the current taxon. Images used in the key are usually displayed on the taxon page for the species.
A few blocks have a link at the top to “Alternate characters,” leading to an “overlapping” block. This is used in cases where the separation of taxa can follow different paths (e.g., a more recently developed matrix block to replace an older dichotomous section).
Two branches meeting in one block
This happens very rarely. For example, the first block of the key to the subfamily Pseudophyllinae can be reached from the section separating the subfamilies of all Tettigoniidae as well as from the section of Neotropical Tettigoniidae only. Moving higher in this block only leads to the all-Tettigoniidae section, and the section on Neotropical subfamilies can only be re-entered separately from the key entry page.
The construction of keys is an ongoing project which currently covers about ten percent of the taxa down to species level. Many sections of the key are already connected at higher ranks, thus comprising one single network. Since different parts of the keys are developed by different people, there can be certain variations in design. And although various parts are still under construction, some partially useful blocks are already shown with an “under development” note.