48 IMPORTED PARASITES. 



Lest any one should think that the figures and diagrams as 

 given are fanciful, and the result of pure speculation, it is well 

 to state in the beginning that they represent, as accurately as the 

 available information will permit, the progress of Monodon- 

 tomerus in the field. The territory covered is not quite as ex- 

 tensive as indicated by the first diagram, owing to the fact that 

 a large part of it is, or would be, open sea; but the recovery 

 of the parasite from the field indicates that it has spread at 

 ,a rate of approximately 10 miles annually to the west and north, 

 and that its increase, which was about twenty-five-f old ' during 

 the summer of 1909, has been maintained at that rate since its 

 liberation. It is not known exactly how many of the parasites 

 were liberated originally, the notes which were made at that 

 time apparently having been lost. Tentatively, the figures are 

 set at 1,000. 



The rate of dispersion, provided it was dependent upon the 

 activities of the insect, and not upon chance or accidental agen- 

 cies, would be about as rapid during the first year from a colony 

 of 1,000 as though it were very abundant. The territory covered 

 by the insect during the six years would therefore be represented 

 by a series of six concentric circles, the smallest of which would 

 have a radius of 10 miles, and each of the 9thers of multiples 

 of 10 up to 60. The area given in acres, and for convenience 

 sake in round numbers, over which the insect would range each 

 year from the first to the sixth, respectively, would be as indi- 

 cated in Diagram I. 



Increase numerically, at the rate of twenty-five-fold annually, 

 would be at a very much more rapid rate, and is indicated by 

 the several squares in Diagram II. It would be impossible to 

 illustrate this increase diagrammatically for the entire six years 

 without the use of a large chart, because the square which would 

 indicate the number of the insects which would result from the 

 sixth year's increase would have sides between 3 and 4 feet long. 

 The figures for six years would be : — 



1906, iOOO 



1907, 25,000 



1908, ... 625,000 



1909, ... 15,625,000 



1910, 390,625,000 

 1911' 9,725,625,000 



