65 



The winters of 1861 and 1862, the years of the serious outbreaks 

 in New York and New England, though not particularly severe in the 

 sections above mentioned, were by no means noted for mildness. It 

 seems doubtful, therefore, if the causes leading to the invasion of the 

 present year would carry us farther back than the spring months, a 

 statement strongly substantiated by our own observation. 



Starting, then, with the month of March we search for some meteoro- 

 logical element which might affect the increase of the Grain Aphis, and 

 which appears both in the present season and also in 1861 and 1862. 



T.vble H.— General weather conditions in various localities during years of great abun- 

 dance of Grain Aphis. 



Locality. 



Tear. 



March. | April. 



May. 



Jane. 





(1861... 



(1862... 

 1889... 

 1889 . 



C Cool | Cool 



\ Average . j Wet 



C Cool j Cool 



\ Wet ! Wet 



C Warm . . . j Warm 



I Dry j Dry 



Cool 



Wet 



Cool 



Di-y 



Cool 



Dry 



Cool. 

 Dry. 





Cool. 

 Dry. 

 Cool. 





Wet. 

 ^Cool. 











1 





^Wet. 



The weather conditions as relating to New York and New England 

 for 1861 and 1862, as given in Table H are based upon reports contained 

 in the Country Gentleman for these years. Those for Indiana are based 

 on the reports of the State Weather Service, and the data for western 

 New York, for 1889, was given me by Prof. James Troop, Horticultural- 

 ist of the Indiana Experiment Station, who visited Livingston County 

 in July. 



From Table I, taken from Indiana Weather Service reports, it will be 

 observed that during March and April the temperature was considera- 

 bly above the normal, with the precipil ation during this time below the 

 average. On the other hand, the temperature of the months of May 

 and June was much below the normal, with, as indicated by Table I, pre- 

 cipitation above the average. By referring to Table K, however, it will 

 be observed that about half of the precipitation of May fell on the 29th 

 and 30th of the month, thereby changing the apparent state of affairs, 

 and practically throwing May into the dry period. 



We have stated that the outbreak of the grain Aphis became con- 

 spicuous in southern Indiana and Illinois in May. It is also true that 

 they reached their maximum numbers during the very last of this month 

 and early June. In other words, they appeared during cool, dry weather, 

 and disappeared in cool, wet weather. Thus far the old theory of ento- 

 mologists, that wet weather is detrimental to their increase appeared 

 true. 



But it is also true, that while in southern localities they were disap- 

 pearing during a wet period, in central and northern Indiana and 

 western New York they were rapidly gaining in numbers, under pre- 

 cisely similar conditions. 

 23479— No. 22 5 



