TWO YOUNG NATURALISTS. 115 



so that the creature is able, when at the bottom of the 

 water, to breathe the air at the surface. Gastro- 

 philus, belonging to the (Estridae ; these lay their 

 eggs amongst the hairs of horses, and the animal, 

 when licking the spot, detaches them and swallows 

 them, and the larvae, developing in the stomach, are 

 well known under the name of bots. And here are 

 the gnats, with whose annoying bites you have been 

 long familiar. 



" Here, too, is a preparation exhibiting the very 

 complicated instruments they use for this purpose. 

 But still more wonderful are the metamorphoses of 

 these creatures. 



" Before becoming an aerial animal, the gnat, or 

 rather its larva, is a little worm of strange form, 

 with a complex arrangement of bristles, and inhabit- 

 ing pools and stagnant waters. 



"When undergoing its final transformation the 

 pupa rises to the surface of the water, and remains 

 there until the swollen part of its outer skin dries 

 and splits ; the perfect insect then raises itself 

 into an erect position by gradually dragging itself 

 out of the skin, which meanwhile floats and serves 

 as a boat, the erect insect being like a little mast 

 and its wings like sails : truly a wonderful and fragile 

 skiff. 



" In addition to great skill the creature requires 

 good fortune to bring this delicate operation to a 



