APHIS-LION FLY. 333 



of, are distinguished by this peculiarity. We 

 behold a very little insect emerge from the pupa- 

 case, and in a quarter of an hour we are astonished 

 to find it has grown to a great fly ! This sudden 

 increase appears the more marvellous, because 

 during this period the insect takes no nourish- 

 ment. The wings of this insect, when it is just 

 born, are not more than one-tenth the size they 

 acquire in that short space of time. The insect 

 is to all appearance firm and plump, and offers 

 a ridiculous contrast to the tiny pupa-case out 

 of which it has emerged. It appears probable 

 that this sudden enlargement is to be accounted 

 for by the insect filling itself with air, and thus 

 causing the various parts so closely packed to- 

 gether, and fitted into one another, in the pupa, 

 to be expanded. The experiment which puts 

 this idea to the test is a very simple one; we 

 need only prick the body of the insect with a fine 

 needle, and we shall hear a slight sound produced 

 by the escape of the air ; and in a few seconds 

 the body of the creature shrinks to its former 

 dimensions. It appears, indeed, that the body 

 of the insect is actually larger at this time than 

 at a subsequent period of its life, when it becomes 



