MOSQUITOES, SILKIVORMS, AND DRAGON-FLIES 23 



which is the kind of sight possessed by almost all insects 

 and crustaceans (crabs, lobsters, crayfishes, etc.), but by 

 no other animals, is called mosaic vision, and cannot be 

 so exact or truthfijl as our own. 



Examine the mouth of the dragon-fly and notice the 

 large flap-like under lip which folds over the opening, and 

 behind it the strong brown jaws. 



Make a drawing from dorsal view of an adult dragon- 

 fly with wings outspread. Make a drawing of the head 

 from front view. 



Egg-laying. — If you watch dragon-flies darting over a 

 pond in summer occasionally some may be seen to swoop 

 down quite to the water's surface and to strike it repeat- 

 edly with the tip of the abdomen. These are laying eggs, 

 and each time the water is touched a few eggs are liber- 

 ated and sink slowly to the bottom. If one of these ovi- 

 positing females can be caught alive the egg-laying may 

 be observed and the eggs obtained for the school aqua- 

 rium by holding the dragon-fly by the wings and touch- 

 ing the tip of her abdomen to the surface of some water 

 in a saucer. The eggs should then be poured into the 

 aquarium (for directions for making simple school aquaria 

 see p. 332) where, if all goes well, they will hatch into 

 young dragon-flies. But as this hatching will not occur 

 until late in the summer, and as the young dragon-flies, 

 called nymphs, grow very slowly and do not change into 

 winged adults for about a year, it will be better to find 

 nymphs in the pond and stock the aquarium with these 

 already partially developed individuals. 



Nymphs. — With a rake or stout water-net (see p. 335) 

 scrape over the bottom of a pond and find in the mud 

 and slime drawn out a number of flattened, heavy- 

 bodied, broad-headed, six-legged creatures like the one 

 shown in figure 12. These are the nymphs of dragon- 

 flies. Each nymph will have on its back four conspicu- 



