I.] METAMORPHOSES OF INSECTS. 21 



known to fishermen. The larvae (PL IV., Fig. i) are 

 semi-transparent, active, six-legged little creatures, 

 which live in water ; having at first no gills, they re- 

 spire through the general surface of the body. They 

 grow rapidly and change their skin every few days. 

 After one or two moults they acquire seven pairs 

 of branchiae, or gills, which are generally in the form 

 of leaves, one pair to a segment. When the larvae 

 are about half grown, the posterior angles of the two 

 posterior thoracic segments begin to elongate. These 

 elongations become more and more marked with 

 every change of skin. One morning, in the month 

 of June, some years ago, I observed a full-grown 

 larva, which had a glistening appearance, owing to 

 the presence of a film of air under the skin. I put 

 it under the microscope, and, having added a drop 

 of water with a pipette, looked through the glass. 

 To my astonishment, the insect was gone, and an 

 empty skin only remained. I then caught a second 

 specimen, in a similar condition, and put it under 

 the microscope, hoping to see it come out. Nor 

 was I disappointed. Very few moments had elapsed, 

 when I had the satisfaction of seeing the thorax open 

 along the middle of the back ; the two sides turned 

 over ; the insect literally walked out of itself, unfolded 

 its wings, and in an instant flew up to the window. 

 Several times since, I have had the pleasure of wit- 

 nessing this wonderful change, and it is really won- 

 derful how rapidly it takes place : from the moment 

 when the skin first cracks, not ten seconds are over 

 before the insect has flown away. 



Another family of Neuroptera, the Dragon-flies, 



