6 THE AMERICAN MONTHLY [Jannaiy, 



the lesser parts are as well. The legs consist of a many-jointed 

 distal-position tarsus bearing two claws at the tip and of a large 

 tibia and femur, but the femur is joined to the body by a long joint, 

 not a short one as in the grasshopper. The wings, too, are on the 

 meso and meta-thorax, the prothorax being grown to the nieso- 

 thorax. The mouth-parts, too, present the same parts, viz., 

 lips and mandible and maxillce, though not like those of the grass- 

 hopper in detail. 



These comparisons can be extended to the internal anatomy of 

 these specimens, and we find that the organs there located cor- 

 respond in position and relation with the various systems of the 

 grasshopper ; they can be extended beyond the series here takeii 

 up to a vast number of other such animals, and in them all the 

 same principles prevail. But it is not possible to demonstrate this 

 plan of body among all animals dwelling together. Thus the 

 spider, slug, saw-bug, and many other animals can be found where 

 crickets live, and yet these bodies cannot be analyzed into such 

 parts as are found in the forms just considered. The spider, for 

 instance, has a body which is divided into two regions ; has no 

 compound eyes and four pairs of simple eyes ; has no antennas, 

 no wings, no mouth-parts, no distinct head ; has four pairs of legs 

 used for walking, and two pairs of appendages in front which find, 

 no compeer among the animals we are studying. Hence the plan 

 we have discovered is a somewhat exclusive one ; all animals 

 which possess it we assign to a group we call a class^ called in- 

 sects, while we regard the various sorts under the class as orders. 

 If we compare the katydid with the other insects we have studied, 

 we shall find it considerably more like the grasshopper and cricket 

 than any others, and these, together with the roach and others, 

 make up the order Orthoptera. In the same one we can see that 

 the potato-bug, firefly, pea weevil, lady-bug, and many other very 

 familiar animals are all somewhat like the May-beetle, and belong 

 in a difterent order from the Orthoptera., while ants and bees go 

 with the wasp, and the mosquito and fly belong together. Orders 

 are divided inio families, and these again into genera., and these 

 into species. Each of these groups has its name, and in speaking 

 technically of any insect or any other animal we do so by giving 

 the name of the genus and species to which it belongs. The de- 

 partment of zoology which is devoted to such comparisons as this 

 is called systematic zoology or classification. 



There are still other departments of zoological study of which 

 we can here do little more than to mention two which have ref- 

 erence to the distribution of animals over the earth's surface or 

 geographical distribution and the date of the appearance of ani- 

 mals in the progress of the geologic history of the earth, or paheo- 

 zoology. The genera and species of animals are often rather 

 local in their geographical range. Northern Europe and North 

 America both have the same genera of grasshoppers, but have 

 few if anv of the same species, while some families, on the other 



