FEMALE. LEPIDOPTERA AT LIGHT TRAPS 
By W. B. Turner 1 
Scientific Assistant, Cereal and Forage Insect Investigations, Bureau of Entomology, 
United States Department of Agriculture 
INTRODUCTION 
It appears to be the generally accepted theory that in the Lepidoptera 
practically all individuals taken at a light trap are males, and that of 
the few females so captured all have oviposited previously. During the 
summer of 1916 extended observations were made at the Hagerstown, 
Maryland, field station of the Bureau of Entomology in an effort to secure 
some definite information as to the relative proportions of the sexes of 
moths attracted to the light and the percentage of gravid females among 
those so taken. The purpose of this paper is to give a brief account of 
the methods employed to obtain material and a summary of the facts 
brought out by a detailed examination of such material. 
The attracting light used was an arc lamp of 300 candlepower hung in 
an inverted truncated cone of heavy tin. One-half of the cone which 
would otherwise encircle the lamp vras cut away; the narrow (lower) 
end of the cone was fitted in the circular opening in the top of the trap. 
Immediately below this opening are arranged several plates of glass at 
angles to direct the moths downward into the body of the trap. The 
trap is 12 by 14 inches and 20 inches high. Two sides are of wire mesh, 
the other sides and the top and bottom being of wood. To kill the cap¬ 
tured insects, the trap was placed in a tightly constructed box with a 
small vessel of carbon disulphid placed at the top of the trap. 
The individuals of some twenty-odd species were preserved in alcohol, 
with the date of each collection. Later these were determined as to 
sex and the number of males and females tabulated for each date. The 
females were carefully dissected and tabulated as to the stage of ova 
development. 
1 The writer wishes to express his appreciation of the assistance given by Mr. Harry E. Parker, of the 
Hagerstown station, who separated the individuals of Caenurgia into the two species represented; and to 
acknowledge the help received from other men of the station. 
(13s) 
Journal of Agricultural Research, 
Washington, D. C. 
od 
Vol. XIV, No. 3 
July is, 191S 
KeyNo.K-W (#7 
