Tools for Identifying plants and animals: a brief history

Many people often want to identify a plant or animal. Some need this information for important practical purposes, such as identifying mosquitoes or other insects that can carry human or plant diseases; or identifying new invasive weeds. Others, such as amateur entomologists or botanists simply want to know the name of a specific insect or plant.

There are several ways in which assistance for such identification needs can be met.   One option is to seek help from an expert. Where this is not possible, alternatives exist such as published field guides, such as a bird book that helps to identify a bird by flicking through images of birds.

In many other cases, however, there is a limit to the usefulness of field guides and image galleries in identifying species. For instance, in Australia, since there are well over 1,000 Eucalyptus and Wattle species, identifying a species of Eucalyptus or Wattle that you come across, using a field guide based on images of these tree species, would be very tedious. The prospect of identifying insect species via a field guide of images is likely to be even more difficult.

This is by no means a new problem. Since the time of Linnaeus (1707 – 1778), naturalists and taxonomists have been aware of the need for a more systematic approach to taxonomic identification. The answer was to develop what are called dichotomous keys, and many thousands of these decision support tools have been developed and published since this time. 

What are dichotomous keys?

Dichotomous or pathway keys consist of a series of linked statements (generally couplets) that describe certain features. An example, showing part of a pathway key to identify which Order an observed insect belongs to, is provided below.

An example: Part of a dichotomous key to Insect Orders

1(a) Well developed wings present, though often folded along body and inconspicuous – 2.
1(b) Wings absent, or present only as small, functionless pads or scales – 14.

2(a) One pair of wings present – 3.
2(b) Two pairs of wings present; hind wings may be concealed beneath protective forewings – 4.

3(a) Forewings membranous; hind wings reduced to tiny club-like structures (halteres) – Diptera
3(b) Hind wings large, membranous; forewings reduced to tiny, strap-like structures – Strepsiptera

4(a) Forewings hard, opaque, in repose forming covers for hind wings; forewings entirely without branching veins or only at apex – 5.
4(b) Forewings either transparent or with branching veins over most of surface, or not forming covers over hind wings – 8. ... Etc.

In working through this key, if the statements 1(a), 2(a) and 3(a) above match the features of the specimen, it is identified as being a fly, in the Order Diptera. Further keys would be needed to get a more precise identification – to family, genus, species. 

Since numerous dichotomous keys exist and are still published in books and journals, digital technology has enabled these keys to be published online, allowing users to follow a pathway of characters (often illustrated) by moving from one web page to the next. In practice, however, a significant problem with dichotomous keys is the ‘unanswerable couplet problem’, where the user cannot decide which couplet statement is correct for the specimen in question? For instance, one node might include ‘flowers red’ or ‘flowers white’: if the plant is not flowering at the time, progress through that key may have to stop there.

While a dichotomous key software program (Lucid Phoenix) incorporates features to get around this problem, an alternative and more user-friendly key system, only made possible with software and hardware developments, is the matrix key system.

Matrix keys

As the name suggests, unlike the pathway structure of Dichotomous keys, the basis of this key system is a tabular database where the columns consist of species within a genus, for example, and the rows consist of features and states that describe the morphological and other characters associated with this set of taxa. The author of the key scores each cell in the matrix to indicate whether that feature/state is found for specimens of that species: although other attributes can be included, such as common or rare, whether a feature state can be misinterpreted. An example of part of a scored matrix for a key to Insect Orders is shown in the Figure below.


Key to Insect Orders example matrix data (from the Lucid Builder)


The data incorporated in this matrix is then converted to a key. Unlike the dichotomous pathway key, this “matrix” tool or key allows the user to decide the order in which features of the specimen to are dealt with; generally, selecting first those features that are most easily distinguished. As users select those feature states they think are exhibited in the specimen to be identified, they either end up with one scientific name or a short list of taxa that match the feature states selected.

Since the late sixties, several software platforms for constructing matrix keys have been developed, the Lucid suite of software being one of them. First developed at the University of Queensland some two decades ago, the Lucid suite of software is now managed by the original developers, operating through a spin-off, Brisbane based company – Identic Pty Ltd.

The Lucid Suite of Software

There are three main software programs that enable Lucid matrix keys to be developed and deployed:

Lucid Builder – the development program used by an author to build a key.

Fact Sheet Fusion (FSF) – a program to facilitate the rapid generation of standardized fact sheets (including text, images, etc) that provide information and images regarding the entities included in a Lucid key. FSF fact sheets can be delivered in HTML, PDF and/or XML format.

Lucid Players – provide the software platforms giving users access to Lucid identification and diagnostic tools. There are two player platforms:

Details of a range of Lucid Mobile apps can be viewed at the app stores:

Available on Google Play Store

Available on Apple iTunes



Problems for which Lucid tools have been developed

Over the past 20 years or so, taxonomists, agronomists and other key authors have used Lucid software to provide their target audience with support in three main, decision making fields.

The original and most common purpose has been to provide decision support for those attempting to identify a plant or animal, whether it be quarantine officers, ecologists, natural resource managers or students. In practice, Lucid tools can be developed for any identification purpose: for example, ecologists and others in Ontario, Canada can access a Lucid Mobile app to help in identifying different ecosystem types, while another Lucid tool was developed to help geology students identify 80 types of minerals.

A second use for Lucid tools has been in providing help to those concerned with diagnosing disorders in agricultural crops, mostly based on crop symptoms. Crop consultants, government advisors and farmers are using Lucid Mobile apps to make their diagnosis in various crops, such as rice, sweetpotato, wheat, canola, tomatoes, brassicas, etc. An example in the medical field is the use of the Lucid Mobile app for diagnosing oral ulceration: this provides a teaching tool for university students.

Lucid tools have also proved useful for to a third decision making paradigm, concerning the choice of a suitable plant for a specific situation and purpose. A Lucid plant selection tool requires a different approach. In this case, the list of entities in the Lucid key are potential crops or cultivars, while the features include such physical details of the farm site, such as altitude, rainfall, soil type, etc., as well as the specific objectives that a farmer might have for growing these potential crops. The major, international project that started in 2005 resulted in the creation of a Lucid-based selection tool for tropical forages. This Lucid tool has recently been updated and deployed as a mobile app.  

A Quick Introduction: Key to Insect Orders

Insect Orders Splash ScreenInsect Orders Home ScreenOne of the first Lucid keys developed at the University of Queensland over 15 years ago was a key to Insect Orders. The purpose in building the key was to help entomology students, who were required to collect insects, and determine to which Insect Order (of 32) each collected insect belongs, whether it is to the Order – Coleoptera (beetles, weevils and ladybirds), Hymenoptera (Ants, bees and wasps), etc.

Originally developed as a CD product, this key has recently been revised and updated as a Lucid Mobile app, as illustrated here. On opening the app, the user sees the content list – consisting of a general introduction to Insect Orders, a link to open the key, a brief description on how to best use the key, and a direct link to the fact sheets for all the 32 Orders.

Clicking on the key symbol opens the Lucid key, showing the Features panel, consisting of 21 features. Each Feature has specific states. In this case, the wing shape feature has been opened, showing the three possible states of this feature. (Note this feature will not be visible if the user had opened the previous feature “Number of Wings” and selected the state “Absent”, rather than states for two or four wings).


Insect Orders Features ScreenInsect Orders entity screen

Insect Orders example fact sheetBy working through the key, the number of Orders remaining is reduced and those remaining can be viewed at any stage by swiping to the left. The details for each Order can then be viewed by clicking on that specific Order: the fact sheet and images for that Order are displayed, as shown for the Order Coleoptera. 

The text description for that Order can provide further help in determining whether the specimen belongs to that Order, as can the thumbnail and enlarged images of different insects within this Order.

Insect Orders example image view