. Bulletin of the Department of Agriculture. Agriculture. pM BULLETIN No. 276 swf^Wu Contribution from the Bureau of Entomology L. O. HOWARD, Chief. W^rtt 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. Page. 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 Descripti
. Bulletin of the Department of Agriculture. Agriculture. pM BULLETIN No. 276 swf^Wu Contribution from the Bureau of Entomology L. O. HOWARD, Chief. W^rtt 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. Page. 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 Page. Generation experiments 27 Ilatching 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 injurious 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 impo
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