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Identification Key to Bats Most Encountered by Humans in Houses

Use of Key

As a tentative means of identifying animals, keys have been devised that use arbitrary, selected characteristics that should be readily distinguishable. However, keys are extremely fallible, and specimens are not always easily identifiable. To use the key, start at number 1 on the left side of the page. There will be two contrasting statements. Select the one that best fits your bat. Then refer to the number or name at the right side of the page. If it is a number, look for this number on the left; again there will be two statements. Proceed as before remembering that it is important to consider each of the two alternatives; one should fit the bat in hand and lead to another pair of alternatives or the name of the bat. The figure that refers to a number should assist in making your decision. The figure that refers to a name should reasonably resemble the specimen to be identified. If it does not, try again. It is easy to select the wrong alternative at some point and the identification will then be erroneous. If you cannot identify the bat it may be necessary to send it to the nearest museum, zoo, or public health laboratory.

Identification Key

1.  About half the tail extends beyond tail membrane; face bare; lips wrinkled; 
    ears close together at base but not joined (Fig. 26)..Tadarida brasiliensis

2.  Tail completely enclosed within tail membrane; face furred; lips not 
    wrinkled; ears widely separated (Fig. 25).................................3
    
3.  Ears large, projecting upward, 28 mm (1.1 in.) from base to tip; nose 
    pugged or pig-like (Fig. 28).............................Antrozous pallidus
    Ears not large, do not project upward, less than 25 mm (1 in.) from base to 
    tip; nose not pugged or pig-like..........................................4
    
4.  Tail membrane upper surface well furred, at least front half, hair tips or 
    hair usually silver-tipped (Fig. 29 and Fig. 31)..........................5
    Tail membrane upper surface naked or sparsely furred; hair tips or hair not 
    silvertipped (Fig. 2, Fig 25).............................................7
    
5.  Hair black (Fig. 29)..............................Lasionycteris noctivagans
    Hair red orange, yellowish................................................6
    
6.  Ears conspicuously black-edged with patches of yellow hair inside (Fig. 31)
    ..........................................................Lasiurus cinereus
    Ears not black-edged, inside bare or scant-haired (Fig. 30)................
    ..........................................................Lasiurus borealis
    
7.  Size large; wingspread 325 to 350 mm (13 to 14 in.) (Fig. 25)..............
    ...........................................................Eptesicus fuscus
    Size small; wingspread 220 to 270 mm (8.8 to 10.8 in.)....................8
    
8.  Fur on back glossy; hairs on toes long and conspicuous (Fig. 24)...........
    ...........................................................Myotis lucifugus
    Fur on back dull; hairs on toes sparse and inconspicuous (Fig. 27).........
    ...........................................................Myotis Yumanenis