65 



Two hibernating females found producing young on May 30 

 (the first larvas of the season to appear) were surrounded by cells 

 as above described, and several of the first young born from them 

 Vt^ere carefully transferred on a camel's hair brush to similar cells. 

 In this manner two colonies w^ere started from two similar parents; 

 and they were carried thru the season, with a break, however, in one 

 of them, caused by the melting in July of the paraffin which fastened 

 the cell to a limb of the tree. The following diagram, devised by 

 Mr. West, gives a complete view of the generations of the San Jose 

 scale as they were thus reared in the open air at Urbana, 111., during 

 the season of 1908. The oblique lines indicate the growing period 

 of the young insects; the horizontal lines, the period of maturity 

 during which young were produced; and each bent, but unbroken, 

 line represents the entire period of the generation, except that no 

 account was taken of the life of the female after she had ceased to 

 reproduce. An x on the diagram indicates the point of origin of 

 a generation from the first-born young of a brood ; and a z, the point 

 of origin of a generation from the last-born young. The W at the 

 left indicates a hibernating female from which the series originated, 

 and the Ws at the right indicate the groups of hibernating young 

 produced. 



Fig. 1. — Diagram of Annual Generations descending from one Hibernating 

 Female. Urbana experiment. 



