7 Limitations of biological keys
It is important to note the limitations of any key or guide used in species identification. The dichotomous key you used in Activity 1, for instance, is limited in covering only those species of dragonfly and damselfly found in the month of May in the British Isles. (It was initially developed as a dichotomous version for students doing field work on an Open University environment course in mid-May.) There are of course many more species of dragonfly and damselfly that fly later in the year in the British Isles, and globally again there are many more species.
Keys are almost always restricted to a certain group of organisms and often to a certain part of the world. If this wasn’t the case, they would be extremely long and unwieldy. However, these limitations can sometimes lead to problems. For example, mobile species such as dragonflies can sometimes end up far from their normal range and plants can escape from gardens or be transported around the world by humans. In the case of this particular dragonfly key used in Activity 1, climate change over recent years means that there are now additional species turning up more frequently in May that are not covered by the key.