Fishermen hunt the dobsons for bait; so you see they have a hard time in spite of their large size and their strong jaws.
When they have lived nearly three years in the water they crawl out on the bank and hollow out a place under a stone.
Here they lie, apparently dead, but they are not dead.
They are undergoing a wonderful transformation.
It takes about a month for this transformation, or metamorphosis, as it is called, to be completed.
All of our other insect friends have changed gradually from larval to adult form. At each moult they became a little more like their parents, and finally at the last moult, without any resting period, out sprang the perfect insect.
Not so the dobson. It goes into its hole in the bank a larva, almost exactly like the larva that hatched from the egg, only, of course, it is larger. There is no hint of wings. It has no separate thorax and abdomen. Could we see under the bank where it has crept, to undergo its great metamorphosis, we should find, not a larva, but a strange-looking, motionless object.
Here is the picture of one. See its little wing pads. And now it has a thorax and an abdomen.
It seems to have changed and been turned to some hard substance.