OF WASHINGTON. 229 



throughout the region with summer heat exceeding 6,400 C., 

 approximating the upper austral life-zone, and including in gen 

 eral the middle section of the United States, together with south 

 ern Michigan and Wisconsin, and the western half of Oregon and 

 Washington. The records of southern California lead us to ex 

 pect three broods for the region with total summer heat exceed 

 ing 10,000 C., corresponding pretty closely with the lower aus 

 tral life-zone, and covering the cotton belt and most of California. 

 The unexpected occurrence of but one annual brood in northern 

 New Jersey, as opposed to two in northern Illinois and Oregon, 

 and three in California, receives here a valid explanation. Doubt 

 less there are many exceptions within the zonal regions indicated 

 by Dr. Merriam, in the number of broods of this insect ; but, 

 normally, they will probably be found to conform to the zones 

 as indicated ; and, at least, a good basis is furnished for future 

 observations. 



The important economic bearing of the variation in the number 

 of broods of the Codling Moth for the zones as thus approxi 

 mately limited comes in connection with remedial treatment. 



Experience has abundantly shown that where there is more 

 than one annual brood it is the second or later broods that are 

 especially to be feared the damage of the first, except on very 

 early apples, rarely amounting to much. Therefore, in the north 

 ern of these zones, or where there is but one brood annually, the 

 infestation will be slight, because accomplished by the compara 

 tively few female moths which successfully hibernate, and will 

 be comparable to the work of the first brood only of the warmer 

 zones. For the northern zone, spraying, except for the early 

 summer varieties, which will attract the majority of the moths, 

 may prove unnecessary ; while for the middle and southern zones 

 remedial effort is at once more necessary and more difficult of 

 successful accomplishment. 



In discussing this paper, Dr. Merriam stated that the case de 

 scribed by Mr. Marlatt was paralleled by the distribution of the sev 

 enteen and thirteen-year broods of the periodical cicada. Mr. 

 Howard referred to the discussion between Professor Riley and 

 Professor J. B. Smith on the number of broods of the elm leaf- 

 beetle and to the suggestion made by Professor Riley that it would 

 be important to study intermediate points betweenWashington and 

 New Brunswick, N. J., to ascertain where the single-broodedness 

 begins. He thought that the double-broodedness would be found 



