JOURNAL OF AGMCBLTDRAL RESEARCH 



DEPARTMENT OF AGRICULTURE 



Vol. VI Washington, D. C, August 21, 1916 No. 21 , 



LIFE-HISTORY STUDIES OF CIRPHIS UNIPUNCTA, 

 THE TRUE ARMY WORM 



By John J. Davis and A. F. Satterthwait, 



Entomological Assistants, Cereal and Forage Insect Investigations, 



Bureau of Entomology 



INTRODUCTION 



For an insect so commonly injurious and widely known as the army 

 worm (Heliophila) Cirphis unipuncta Ha worth, comparatively little con- 

 cerning its life economy is recorded, and the detailed experiments herein 

 reported represent phases of the more exact studies begun by this 

 branch of the Bureau of Entomology. 



Late in July, 191 4, the army worm appeared in very destructive num- 

 bers in Huron and Sanilac Counties, Mich., and from the progeny of 

 larvae collected in that locality eggs and larvae were obtained with which 

 a series of molting and feeding experiments was started at La Fayette, 

 Ind. The feeding experiments, where exact records of the amount of 

 corn foliage eaten in each instar were kept, are especially interesting and 

 instructive, for it will be noticed that more than 80 per cent of all the 

 foliage eaten during the entire life of the larva was consumed during the 

 last larval instar, which corroborates previous field observations to the 

 effect that army worms rarely become evident and destructive until 

 they are nearly full grown. 



GENERATIONS OF THE ARMY WORM 



During the past year (19 15) Cirphis unipuncta was bred continuously 

 throughout the season from moths collected from May 13 to 15, to deter- 

 mine the average number of generations annually. Moths of C. uni- 

 puncta were first observed at La Fayette the night of May 13 feeding on 

 the honeydew produced by Pulvinaria vitis L-, 1 Lecanium quercifex 

 Fitch, 1 and Callipterus discolor Monl. on white oak, and it is quite likely 

 that these moths were the adults of larvae overwintering in this latitude. 

 Moths were placed in large breeding cages under natural outdoor 

 conditions, and eggs were laid and the larvae first observed on June 7. 



1 Kindly determined for the Bureau of Entomology by Prof. J. G. Sanders. 



Journal of Agricultural Research, Vol. VI, No. ai 



Dept. of Agriculture, Washington, D. C Aug. 21, 1916 



ex K— 40 



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