Novel software developed during the ICT revolution, initially in the 1970s and 80s, provided the opportunity for different matrix-based identification tools to be developed. One of the earliest matrix key programs was the DELTA system, developed during the 1980s at CSIRO in Australia. Two other systems were developed in the 1990s, the Lucid system, initially developed at The University of Queensland, and the Linnaeus identification system, developed at the University of Amsterdam, and now incorporated in Linnaeus NG.
To build a matrix key to insect orders, as shown in the diagram below, information about the two axes (the list of taxa and the list of morphological features important for making an identification) have to be entered in the matrix. The cells in the matrix (denoting a feature/state for a specific insect order) are scored for presence/absence, common/ rare, or misinterpretation (where users are likely to select a feature/state by mistake).
A matrix key for insect orders
Once the data has been incorporated and scored in the key builder, images and supporting text can be linked to the key’s feature/states and taxa, helping users make an identification. When a key is completed, it can be deployed as a DVD, USB, online, or as a mobile app, depending on the builder platform used.
The screen shots below show the insect order key displayed in two different player formats:
(a) the 4-window format for an internet or desk-top player, showing Features – available/selected; Taxa – remaining/discarded; and
(b) the single screen format for smartphones and tablets. 
The mobile app ‘Antkey Mobile’, shown below, is a community resource that includes an online matrix key to help identify invasive, and commonly intercepted ant species from across the globe. Available as Apple and Android versions, the apps enable the full key to be used anywhere, without requiring access to Wi-Fi or a phone connection.
Screen shots taken from the Antkey Mobile App
Matrix keys have also been used to provide diagnostic tools that help growers, crop advisors and surveillance teams diagnose observed symptoms in crops, which may have national or regional biosecurity implications.
