112 THE ANIMALS AND MAN 



urements, colors and markings, and drawings of bill and 

 feet, showing the resemblances and the differences between 

 the downy woodpecker and the hairy woodpecker. These 

 two kinds of woodpeckers are very much alike, but the 

 hairy woodpeckers are always much larger (nearly a half) 

 than the downy woodpeckers and the two kinds never 

 mate together. The hairy woodpeckers constitute another 

 species of bird. 



Genus. — Examine now a flicker (the yellow-shafted or 

 golden-winged flicker in the East, the red-shafted flicker in 

 the West). Compare it with the downy woodpecker and 

 the hairy woodpecker. Make notes referring to the differ- 

 ences, also the resemblances. The flicker is very differently 

 marked and colored and is also much larger than the downy 

 woodpecker, but its bill and feet and general make-up are 

 similar and it is obviously a "woodpecker." It is, however, 

 evidently another species of woodpecker, and a species 

 which differs from either the downy or the hairy wood- 

 pecker much more than these two species differ from each 

 other. There are two other species of flickers in North 

 America which, although different from the yellow-shafted 

 flicker, yet resemble it much more than they do the downy 

 and hairy woodpeckers or any other woodpeckers. We 

 can obviously make two groups of our woodpeckers so far 

 studied, putting the downy and hairy woodpeckers (together 

 with half a dozen other species very much like them) into 

 one group and the three flickers together into another group. 

 Each of these groups is called a genus, and genus is thus the 

 name of the next group above the species. A genus usually 

 includes several, or if there be such, many, similar species. 

 Sometimes it includes but a single known species. That 

 is, a species may not have any other species resembling it 

 sufficiently to group with it, and so it constitutes a genus by 

 itself. If later naturalists should find other species re- 

 sembling it they would put these new species into the genus 



