Page:First course in biology (IA firstcourseinbio00bailrich).pdf/317

 stages: (1) egg, (2) larva, (3) pupa, and (4) imago, or perfect insect (Figs. 136, 137, 138).

—Measuring worm, the larva of a moth.

—Pupa of a mosquito.

, all enlarged.

a, egg on hair of horse (bitten off and swallowed); b, larva; c, larva with hooks for holding to lining of stomach; d, pupal stage, passed in the earth; e, adult horse fly.

The egg stage is one of development, no nourishment being absorbed. The larval stage is one of voracious feeding and rapid growth. In the pupa stage no food is taken and there is no growth in size, but rapid development takes place. In the perfect stage food is eaten, but no growth in size takes place. In this stage the eggs are produced. When there is very little resemblance between the larva and imago, and the pupa is quiescent, the metamorphosis, or change, is said to be complete. When, as with the grasshopper, no very marked change takes place between the larva and imago (that is to say, during the pupa stage, which is active), the metamorphosis is said to be incomplete. By studying the illustrations and specimens, and by thinking of your past observations of insects, determine which of the insects in the following list have a complete metamorphosis: beetle, house fly, grasshopper, butterfly, cricket, wasp.