BEHAVIOR OF PHYTOPHAGA DESTRUCTOR SAY UNDER 
CONDITIONS IMPOSED BY EMERGENCE CAGES 1 
By Walter H. Larrimer 
Entomologist, Office of Cereal and Forage Insect Investigations, Bureau of Ento¬ 
mology, United States Department of Agriculture 
INTRODUCTION 
The Hessian fly, PhytopTiaga destructor Say, has long been recog¬ 
nized in America as a wheat pest ofprimary importance, and even 
before its scientific description by Thomas Say in 1817 it had at¬ 
tracted considerable attentiqn and was referred to under the popular 
name of Hessian fly. Naturally such an insect pest has been the 
subject of much published discussion as well as almost every con¬ 
ceivable type of investigation. Many excellent accounts of the life 
history, food habits, natural enemies, control, and other interesting 
phases in the life of this insect are readily available and therefore 
need not be repeated. Osborn (7) 2 has given a very comprehensive 
treatise on the Hessian fly in America, with a complete bibliography 
of all important papers up to 1898. For contributions appearing 
since that time full references will be found in the Bibliography of 
American Economic Entomology (1,8). 
The determination of the time and extent of the emergence of 
adult flies from flaxseeds under varying conditions has always been 
an important factor in the study of tins phase of the life history of 
the Hessian fly, and particularly in reference to various schemes for 
control.. The present discussion deals with the design of a number 
of emergence cages, and the determination of the relative efficiency 
both as to approach to natural conditions and ability to recover 
emerged flies. 
EMERGENCE CAGES 
Although many types of cages have been suggested from various 
sources, the selection of type, actual design of cages, and accomplish¬ 
ment of results may be considered as original. The six types of 
emergence cages selected were as follows: 
Type A.—Cone-shaped, frame of sheet tin covered with 18-mesh 
pearl screen wire. Base circular, of diameter sufficient (40.6 inches) 
to make it inclose 1 square yard. Altitude 30 inches, and top 
terminating in a sheet-tin cone with 0.5-inch hole at the small end. 
Over this hole is fitted a small screen trap for catching flies that 
emerge from the cage through the hole in the top (fig. 1, A). 
Type B.—Square, base inclosing 1 square yard. Height, 18 inches. 
Frame of 1 by 2 inch cypress, covered with 18-mesh pearl screen wire. 
Top is painted with thin tanglefoot and made to open upward to 
facilitate counting of flies caught on the tanglefoot (ng. 1, B). 
1 Received for publication Oct. 7, 1924; issued October, 1925. 
2 Reference is made by number (italic) to “Literature cited,” p. 574. 
Journal of Agricultural Research, 
Washington, D. C. 
( 567 ) 
Vol. XXXI, No. 6 
Sept. 15,1925 
Key No. K-151 
