Mammals of Indiana: A Field Guide

Use of Keys

29 Use of Keys Taxonomic keys to identify organisms are incorporated into this volume. Keys call on the user to make choices one after the other until an answer, hopefully the correct species, is determined. Keys are meant to help get an answer quickly. The alternative is to look through the descriptions of all of the possiblespeciesuntilyoucometotherightidentification.Keys are of greatest use when trying to decide among a fairly large number of closely related species. The value of keys is that you make only one choice at a time, choosing between two groups of characteristics. For example, if you have a bat in hand and go to the key to bats, you will find the first “couplet” as follows: 1. Interfemoral membrane with hairs above, either completely or on basal half...........................................................2 Interfemoral membrane without hairs above. ....................4 Youthenmakethechoiceaboutthehairontheinterfemoral membrane and move on to the next choice; for example, if you decide the hair is present on the interfemoral membrane, you then go on to couplet #2, which reads as follows: 2. Interfemoral membrane with hair on basal half only......... . .............................................Lasionycteris noctivagans, p. 110 Interfemoral membrane fully haired...................................3 You then determine whether the hair is on the basal half or covers the entire membrane. If it covers the basal half and fits the rest of the couplet, then you have your answer, the silverhairedbat ,Lasionycterisnoctivagans.Youthenchecktheentire description to be sure the rest of the characteristics fit and you have helped confirm your answer. Ifyoudeterminethatyouhave“keyed”tothewrongspecies, then try keying again, looking carefully for any place that you might have gone wrong. Common reasons for “going wrong” in the key are that you do not understand a characteristic, that the material to be identified is of poor quality, or that you try Mammals.indb 29 3/31/10 3:08 PM 30   Naming and Identifying Mammals to go through the key too fast. Often we go wrong when we have “prejudged” what the species is and tend to make the key work in that direction. Using keys is a help or tool and is not fool-proof. Practice in use of the key is of great help. The more different species you have keyed, the better you understand the characteristics. It helps greatly to know some of the species as you use keys, and also it helps to practice by keying some “knowns” through to their correct answers. Mammals.indb 30 3/31/10 3:08 PM ...