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Bird -Lore 



tures, stiffened with branching ribs that make them resemble more or less 

 closely the leaves of certain plants. They are jointed at their attachment to 

 the body and can be moved with greater or less freedom by the insect, the 

 tip of each wing describing a figure 8 in flight. A study of the develop- 

 ment of insect wings shows that they are really nothing but great flat ex- 

 pansions of the sides of two rings of the body, the second and third behind 

 the head of the animal. Their shape varies greatly in different insects, and 

 on it depends the character of the flight in any particular instance. Insects 

 with both pairs of wings broad and of nearly uniform shape and size have a 



PTERODACTYL 



Courtesy of F. A. Lutas 



slow, unsteady flight. This is the case with many moths and butterflies. In- 

 sects of powerful and rapid flight, like the hawk-moths, often seen hovering 

 about flowers in the twilight, have the fore-wings long, narrow and pointed 

 and the hind -wings small. In some of these swift -flying insects, like the 

 flies, — our common house-fly, for example, — the hind-wings are reduced to 

 little rudiments, called balancers, or halteres, which no longer function as 

 wings. Finally, insects with a gliding flight, like the grasshoppers, have 

 small narrow fore -wings and broad, fan-shaped hind-legs. 



The wings of all back-boned animals differ from those of insects in be- 

 ing peculiar modifications of limbs which were originally used for walking, 

 or, in the case of the flying fish, for swimming. They are not mere expan- 



