HEMIPTERA. 175 



out to their full dimensions, and in the course of a few hours the 

 superfluous moisture of the body evaporates, and the insect be- 

 comes strong enough to fly. 



During several successive nights the pupa3 continue to issue 

 from the earth ; above fifteen hundred have been found to arise 

 beneath a single apple tree, and in some places the whole surface 

 of the soil, by their successive operations, has appeared as full of 

 holes as a honeycomb. In Alabama the species under considera- 

 tion leaves the ground in February and March, in Maryland and 

 Pennsylvania in May, but in Massachusetts it does not come forth 

 till near the middle of June. Within about a fortnight after their 

 final transformation they begin to lay their eggs, and in the space 

 of six weeks the whole generation becomes extinct. 



Fortunately these insects are appointed to return only at periods 

 so distant that vegetation often has time to recover from the injury 

 inflicted by them ; but were they to appear at shorter intervals, 

 our forest and fruit trees would soon be entirely destroyed by 

 them. They are moreover subject to many accidents, and have 

 many enemies, which contribute to diminish their numbers. 

 Their eggs are eaten by birds ; the young, when they first issue 

 from the shell, are preyed upon by ants, which mount the trees to 

 feed upon them, or destroy them when they are about to enter the 

 ground. Blackbirds eat them when turned up by the plough in 

 fields, and hogs are excessively fond of them, and, when suffered 

 to go at large in the woods, root them up, and devour immense 

 numbers just before the arrival of the period of their final trans- 

 formation, when they are lodged immediately under the surface of 

 the soil. It is stated that many perish in the egg state, by the 

 rapid growth of the bark and wood, which closes the perforations 

 and buries the eggs before they have hatched ; and many, without 

 doubt, are killed by their perilous descent from the trees. 



There are several other harvest-flies in the United States, the 

 males of which are musical ; but their drums are concealed 

 within little cavities in the sides of the first abdominal ring. One 

 of these is found in Massachusetts, and, though it never appears in 

 such great numbers as the preceding species, it is more common 

 or more generally met with throughout the State. It may be 

 called the dog-day harvest-fly, or Cicada canicularis, from the 



