UNITED STATES DEPARTMENT OF AGRICULTURE 



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BULLETIN No. 276 



Contribution from the Bureau of Entomology 

 L. O. HOWARD, Chief 



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Washington, D. C. 



PROFESSIONAL PAPER 



September 29, 1915 



THE PEA APHIS WITH RELATION TO FORAGE 



CROPS. 



By J. J. Davis, ■ 

 Entomological Assistant, Cereal and Forage Insect Investigations. 



CONTENTS. 



Introduction 1 



Synonymy 2 



Identity of the species occurring in America . 4 



Past history of the pest and its injuries 5 



Character of attack 7 



Effects on cattle of feeding them infested 



clover. 7 



Distribution and origin 8 



Food plants 9 



Description ■ 12 



Life history '. 26 



Field observations 26 



Generation experiments 27 



Hatching of the egg 43 



Molting 43 



Age at which females begin reproducing 45 



Reproductive period 49 



Longevity 49 



Fecundity of viviparous females 49 



Sexual forms 50 



Fecundity of oviparous females 51 



Natural control 52 



Methods of artificial control 54 



INTRODUCTION. 



The periodic occurrence of the pea aphis (Macrosiphum pisi Kalt.) 

 in. unusual abundance on various leguminous crops, more especially 

 red and crimson clovers, vetches, field and garden peas, and sweet peas, 

 has placed it among the important injurious insects of the world, for it 

 is almost cosmopolitan and more or less inj urious wherever found. In 

 Europe it has been the subject of numerous treatises, both from the 

 systematic and economic viewpoints, and its identity has been much 

 confused with other closely related species. In America it seems to 

 have made its first appearance in destructive and noticeable numbers 

 in 1899, although it is known to have been present here for at least 

 two decades previous, and each year since 1899 this aphis has been 

 recorded as injurious in one or more localities in the United States. 



In the present paper we have attempted especially to settle the 

 identity of the species, an important item from the economic stand- 

 point, and to report our extended life-history investigations, together 

 with a summary of all the important facts, both old and new, relative 

 to the life economy of the species. 



98034°— Bull. 276—15 1 



