THE INSECTS OF MAY. 195 



known to fall like snow upon the ground, when the peasants 

 gather them up in heaps to enrich their gardens and farms. 



The Case worms, or Caddis flies (Fig. 234), begin now to leave 

 their portable houses, formed of pieces of leaves, or sticks and 

 fine gravel, or even of shells, as in an European species, and fly 

 over the water, resting on the overhanging trees. 



A few busy Mosquito Hawks, or Dragon flies (Libellula), 

 herald the coming of the summer brood of these indefatigable 

 friends of the agriculturist. During their whole life below the 

 waters, these entomological Herods have slain and sucked the 

 blood of myriads of infant mosquitoes and other insects ; and 

 now in their new world above the waters, with still more in- 

 tensified powers of doing mischief, happily, however, to flies 

 mostly obnoxious to man, they riot in bloodshed and carnage. 



234. Different Forms of Case Worms. 



This is the season to stock the fresh- water aquarium. Go to 

 the nearest brook, gather a sprig or two of the water cress, 

 which spreads so rapidly, a root of the eel grass, and plant 

 them in a glass dish or deep jar. Pour in your water, let the 

 sand and sediment settle, and then put in a few Tadpoles, a 

 Newt (Salamander), Snails (Limnsea, Planorbis and Valvata), 

 Caddis flies and Water beetles, together with the gatherings 

 from a thicket of eel' grass, or other submerged plants, being 

 rich in the young of various flies, Ephemeras, Dragon flies and 

 Water fleas (Entomostraca, Fig. 235), which last are beautiful 

 objects for the microscope, and in a few days the occupants will 

 feel at home, and the aquarium will be swarming with life, 

 affording amusement and occupation for many a dull hour, by 

 day or at night, in watching the marvels of insect transforma- 

 tions, and plant-growth. 



Among the injurious hymenoptera, which abound late in this 



