31 



species most abundant in Brazil lives about thirty years. The 

 seeding is not simultaneous w^ith all plants, but lasts about five 

 years, more and more canes seeding each year, and each cane 

 producing an astonisliing amount of fruit, so that often the 

 ground is covered inches deep with the fallen seed. 



In 1879 ]Mr. Orville A. Derby found an almost universal lack 

 of corn throughout the Province of Parana, Brazil, which was 

 due to an invasion of rats which followed the fruiting of the 

 canes. Each cane bears about a peck of edible seed, resembling 

 rice, which is very nourishing. Durmg the fruiting season the 

 number of canes bearing seed increases each year, and the rats 

 multiply accordingly. The last of the crop of seeds having 

 matured and fallen to the ground, decays. The rats, suddenly 

 deprived of food, begin to migrate and invade the plantation 

 houses, consuming and destroying everything eatable. At corn- 

 planting time the seed is eaten as fast as it can be put into the 

 ground. Mr. Mercer replanted six times in one year, and 

 finally gave up in despair. The rice crop is ruined, and every- 

 thing in the houses in the way of provisions and leather is 

 destroyed if not carefully guarded in rat-proof receptacles.^ 

 Similar plagues of rats occur in Chili, where the cane fruits in 

 the same manner; ^ also in Ceylon, following the flowering and 

 death of tropical underwoods, which fruit in the same way as 

 the cane, but about every seven years. The rats afterward 

 attack coffee plantations and prove very destructive.^ 



Grain growing offers a similar attractive food supply for rats. 

 They can live in the fields in summer and fall, storing up a 

 certain supply of food in their burrows for winter. In open or 

 southern winters they can pick up much waste grain. In the 

 north, their sudden appearance in large numbers in November 

 or December may be due to the approach of winter, which 

 drives many into farm buildings or into villages and cities. 

 Farms •with accumulations of rubbish under, in and about the 

 buildings harbor rats by the hundred in winter, and hay and 

 grain stored m the barns too often furnish them such a liberal 

 supply of food that they may breed in any month of the year. 

 A sudden local appearance of rats in numbers often is due to 

 energetic measures taken by some neighbor to rid his premises 



' Nature, Vol. 20, May 15, 1879, p. 65. s Ibid., Vol. 20, July J7, 1879, p. 266. 



' Ibid., Vol. 20, Oct. 2, 1879, p. 530. 



