188 INSECTS INJURIOUS TO VEGETATION. 



scale-like prominences on their backs, which represent and 

 actually contain their future wings. 



As the time of their transformation approaches, they gradu- 

 ally ascend towards the surface, making in their progress 

 cylindrical passages, oftentimes very circuitous, and seldom 

 exactly perpendicular, the sides of which, according to Dr. 

 Potter, are firmly cemented and varnished so as to be water- 

 proof. These burrows are about five eighths of an inch in 

 diameter, are filled below with earthy matter removed by the 

 insect in its progress, and can be traced by the color and com- 

 pactness of thek contents to the depth of from one to two 

 feet, according to the nature of the soil; but the upper portion 

 to the extent of six or eight inches is empty, and serves as a 

 habitation for the insect till the period for its exit arrives. 

 Here it remains during several days, ascending to the top of 

 the hole in fine weather for the benefit of the warmth and the 

 air, and occasionally peeping forth apparently to reconnoitre, 

 but descending again on the occurrence of cold or wet weather. 



During their temporary residence in these burrows near the 

 surface, the Cicada grubs, or more properly pupae, for such 

 they are to be considered at this period, though they still re- 

 tain something of a grub-like form, acquire strength for further 

 efibrts by exposure to the light and air, and seem then only to 

 wait for a favorable moment to issue from their subterranean 

 retreats. When at length this arrives, they issue from the 

 ground in great numbers in the night, crawl up the trunks of 

 trees, or upon any other object in their vicinity to which they 

 can fasten themselves securely by their claws. After having 

 rested awhile they prepare to cast off" their skins, which, in 

 the meantime, have become dry and of an amber color. By 

 repeated exertions a longitudinal rent is made in the skin of 

 the back, and through this the included Cicada pushes its 

 head and body, and withdraws its wings and limbs from their 

 separate cases, and, crawling to a little distance, it leaves its 

 empty pupa-skin, apparently entire, still fastened to the tree. 

 At first the wing-covers and wings are very small and opake, 

 but, being perfectly soft and flexible, they soon stretch out to 

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



