BUTTERFLIES AND BEES 27 



Thus, locomotion is brought about by means of legs and 

 wings. Both insects breathe through spiracles arranged in a 

 row on each side of the abdomen. Food is in both cases taken 

 in by the mouth ; but the grasshopper has a biting or chewing 

 mouth, whereas the butterfly has a sucking mouth.^ 



22. Development of the grasshopper. If we study the whole 

 life of these insects from the beginning to the end, we shall 

 find some more interesting similarities as well as differences. 

 The mother grasshopper lays her eggs in the ground, where 

 they remain the whole winter. When the young hatch out they 

 look like tiny grasshoppers without wings, and their heads are 



a 



Fig. 10. Red-legged locust (Melanoplus femur -rubrum) 



a, eggs in the ground; b^, young wingless larva; b^, larva molting; c, pre-adult; 



d, adult insect 



rather large in proportion (see Fig. 10). The animal begins eat- 

 ing almost immediately, but for a time it does not increase in 



^When making comparisons between various organisms we must be con- 

 stantly on our guard not to read into our observations more than the facts 

 allow. For example, it is a very easy matter to state what we observe about 

 the mouths of the insects in this way : " The mouth of this insect has biting 

 jaws, since it feeds upon solid food, whereas the mouth of the other is a suck- 

 ing mouth, since it feeds upon fluids." A little thought will show us that it 

 would be just as true to say : "The grasshopper feeds upon solids, since it has 

 a biting mouth, and the butterfly sucks nectar from flowers, since it has a 

 long, sucking mouth." In other words, all we really know, from our observa- 

 tions, is that the structure of each animal somehow fits in with its activities or 

 habits — that each animal uses its organs in its own particular way. We do 

 not know how each kind of animal came to have the structures and habits 

 which we find it to have, or how it came to have the ways of living that it has. 

 There are many attempts to explain what we find, and we shall study some of 

 these proposed explanations later. 



