54 HOW TO USE THE KEY. 
must be careful how he strikes in any where except at the beginning, for a 
false start will soon set him hopelessly adrift. The Key has been tested * 
so thoroughly that there is little danger of his running off the track except 
through carelessness, or misconception of technical terms; but there is no 
excuse for the former, and the latter may be obviated by the Glossary and 
the Introduction, which should be consulted when any doubt arises. Time 
spent upon the Introduction will be time saved in the end. 
§ 94. Now the genus Picus that we found has a number after it, which 
refers to the Systematic Synopsis, where the genera are numbered consecu- 
tively. The running numbers at the top of the pages catch the eye ina 
moment, and enable us to turn directly to Picus, 131. Here we find a few 
remarks, illustrative of the general character of all our species of the genus ; 
and these we see, are six in number. We have now to find out which one 
of the six ours is; and to this end they are analyzed, that is, mapped out 
in groups, in such way that we perceive their most striking features, or 
diagnostic characters, almost at a glance : — 
* Body not banded, streaked nor spotted. 
** Spotted and crosswise banded, but not streaked. 
*** Spotted and lengthwise streaked, but not banded. 
+ Usually 9-10 long; outer tail-feathers wholly white. 
tt Usually 6-7 long; outer tail-feathers barred with black and white. 
The specimen has no transverse bars of color on the body, but a long 
white streak down the back, and a profusion of white spots on the wings and 
their coverts ; it is not over seven inches long, and has the outer tail feath- 
ers black and white; so that we know it comes under ***t+. As there 
is but one species given there, our bird is at last identified. It is the 
downy woodpecker, Picus pubescens. The term pubescens, at the end of 
the descriptive paragraph, is the specific name, which, joined with the gen-— 
eric name, Picus, constitutes the scientific designation of the species, as ex- 
plained in the Introduction, p. 13. In this case of the downy woodpecker, 
no full description appears, merely because the bird “is exactly like P. 
villosus” (the preceding species) except in the diagnostic points of size and 
barred rectrices ; but in general, a concise specific description will be found. 
These descriptions are not always, or even usually, full and complete ; 
being designed simply to discriminate the several species of the same genus, 
or to certify that the student has discovered the right species, if there be 
but one under the genus. But since mere identification of a specimen is not 
all that we may desire, many other particulars are really given. Thus we 
discover that the downy woodpecker inhabits Eastern North America, and is 
replaced in the West by a variety closely resembling it. We discover its 
exact relations to its congener, P. villosus, and of both these to the other 
*In the cases of over nine-tenths of the genera, by actual comparison with the specimens themselves, and 
found to give accurate results. It is just possible, that an occasional immature specimen, or one offering un- 
usual deviation from the normal standard, cannot be determined by the Key. 
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