128 EVENINGS AT THE MICROSCOPE 



great thorax, and, bending under it, ends in an exces- 

 sively delicate, transparent, swimming- plate. It is this 

 curving abdomen, with its terminal swimmer, and its back- 

 ward strokes in swimming, that constitute the resemblance 

 to a prawn or lobster. 



If we now bring a low power with the reflected light of 

 the Lieberkuhn to bear on it, we shall see the progress 

 the animal has made in this its change of raiment. The 

 thorax shows on its sides the future wings, crumpled and 

 folded down, the nervures of which we can discern dis- 

 tinctly. The elegant little head, too, can be well made 

 out; its eyes, now perfectly marked with the numerous 

 hexagonal facets that belong to the matured organs of vi- 

 sion in these creatures; its antennas, like slender rods, folded 

 down side by side along the inferior edge of the thorax; 

 the short palpi lying outside these; and within, both the 

 lancets and piercers that are destined to subserve the 

 blood- sue king propensities of our sanguinary little subject, 

 when it attains its winged condition all incased in the 

 transparent pupa skin that lies like a loose wrapper around 

 everything. 



The extremity of the abdomen has now nothing to do 

 with respiration, and hence it is never brought to the sur- 

 face of the water, as it was constantly before. The little 

 animal still habitually lives in contact with the air, coming 

 up to it with rapid, impatient jerks, whenever it has de- 

 scended; but it is invariably the summit of the thorax that 

 is uppermost, and when the creature rests it is this part 

 that touches the surface. 



Why is this ? you ask. Look, and you will see why. 

 From the summit of the thorax project two little horns, 

 which, under the microscope, are seen to be clear trumpet- 



