. Bulletin of the Department of Agriculture. Agriculture. j>-^'^w 1 BULLETIN No. 841 Contribution from the Bureau of Entomo'ogy L. O. HOWARD, Chief. jTLiPf^'^'OT- Washington, D. C. PROFESSIONAL PAPER May 7, 1920 THE WESTERN GRASS-STEM SAWFLY By C. N. AiNSLiE,' Entomological Assistant, Cereal and Forage Insect Investigations CONTENTS Introduction 1 History 2 Food plants 8 The egg 9 Development ot the egg 10 The larva 11 The pupa 16 The adult 17 Oviposition 19 Key to North American species of 22 Natural control 23 Artificial control 24 Cephus pygmaeus (L.) 26 Description -. 27
. Bulletin of the Department of Agriculture. Agriculture. j>-^'^w 1 BULLETIN No. 841 Contribution from the Bureau of Entomo'ogy L. O. HOWARD, Chief. jTLiPf^'^'OT- Washington, D. C. PROFESSIONAL PAPER May 7, 1920 THE WESTERN GRASS-STEM SAWFLY By C. N. AiNSLiE,' Entomological Assistant, Cereal and Forage Insect Investigations CONTENTS Introduction 1 History 2 Food plants 8 The egg 9 Development ot the egg 10 The larva 11 The pupa 16 The adult 17 Oviposition 19 Key to North American species of 22 Natural control 23 Artificial control 24 Cephus pygmaeus (L.) 26 Description -. 27 INTRODUCTION The western grass-stem sawfly (Cephus cinctus Norton) (fig. 1) is in many ways one of the most interesting and important insects that has attracted the especial attention of economic entomologists in recent years. It is a species native to the Laiited States and has been gradually coming into prominence since the beginning of the present centm-y by reason of the change which the feeding habits of the larvae have been undergoing subsequent to its discovery. Originally a grass feeder, it is becoming a serious menace to the grain growers of the Northwestern States because of its acquired appetite for small grains, within the stems of which it now subsists. Such changes of diet are probably occurring everywhere with greater frequency than formerly was deemed possible, especially among the phytophagous insects of the Middle West. When given a 1 The writer wishes to express his appreciation of the assistance afforded hy Messrs. J. C. Crawford, A. B. Gahan, and S. A. Rohwer, of the Bureau of Entomology, in the preparation of paper, the two former in determining parasitic material reared during the progress of the studies of the sawfly, the latter in making a critical examination of a large series of sawfly individuals reared or collected from various parts of North America, and for furnisliing detailed descriptions of Cephus cinctus besides a key to the North Americ
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectagriculture, bookyear
