HOW TO KNOW THE BUTTERFLIES 



termed. As the ommatidia are closely massed 

 together, the outer surfaces of each is hexagonal 

 in outline like the cells of honeycomb (Fig. 3). 

 Eyes of this type are termed compound. 



Many insects have simple eyes, or ocelli, in 

 addition to compound eyes ; but ocelli are very 

 rarely found in butterflies. 



The antennce are the long, more or less thread- 

 like appendages that project from the upper part 

 of the head ; they are what children are apt to 

 call the horns of the butterfly. 

 Each antenna consists of many 

 segments or ringlike divisions. 

 The antennas are supposed to 

 bear the organs of smell. In 



Fig. 3. — Part of a com- 



pound eye, greatly butterflies the terminal seg- 

 magmfied. ments of the antennas are en- 



larged so as to form a club. 



The mouth-parts of butterflies consist chiefly 

 of a pair of palpi and the sucking organs, max- 

 illa. The palpi are the jointed organs that pro- 

 ject forward from the lower side of the head. 

 They vary greatly in length in different families, 

 and vary in the relative length of their segments, 

 so that use is made of them in the classification 

 of butterflies. The maxillae are greatly modified 

 jaws, which are so lengthened that they have lost 



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