212 



INSECT CALENDAR. 



senting a cylindrical structure, not unlike a small cartridge. 

 They commence hatching in March, but it requires a range of 

 temperature above 60 F. to bring them to maturity, and under 

 such conditions they become fledged in thirty-three days, and in 

 from three to five days after they enter upon their migratory 

 flight. 



&quot;Their instincts are very strong. When food becomes scarce 

 at one point, a portion of them migrate to new localities, and 

 this movement takes place simultaneously over large areas. In 



264. Seventeen Year Locust, Eggs and Pupa. 



their progress they stop at no obstacle they can surmount. In 

 these excursions they often meet with other trains from an 

 opposite direction, when both join in one. 



&quot;The insects are voracious, but discriminating in their choice 

 of food, yet I know of no plant they reject if pressed by hunger ; 

 not even the foliage of shrubs and trees, including pine and 

 cedar.&quot; 



During this month the Seventeen-year locust (Cicada septen- 

 decim of Linnaeus, Fig. 264) has disappeared, and only a few 

 Harvest flies, as the two other species we have are called, raise 

 their shrill cry during the dog-days. But as certain years are 



