202 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
been damaged is not in itself an accurate estimate but we believe such 
reports have sufficient merit to warrant their being requested, especially 
where the entomologist has a large list of active farmer cooperators. 
A questionnaire should be furnished which can be filled out in short 
concise statements. 
Having in hand a knowledge of the infested areas, the degree of in¬ 
festation, the production of such areas during immune periods, and the 
production during infestation and the action of other limiting factors, we 
believe that the entomologist may compile a statement which, after 
comparison with the: ndividual estimates of county agents and fanner 
cooperators, will be a close estimate of the damage done. We believe 
that such an estimate should present the damage done in terms of per¬ 
centage of crop loss rather than monetary loss. 
THE APPLICATION OF STATISTICAL METHODS TO THE 
DETERMINATION OF ABUNDANCE OF AND 
DAMAGE BY HESSIAN FLY 1 
By W. H. Larrimer, Entomologist, U. S. Bureau of Entomology, 
West Lafayette, Indiana 
Abstract 
The discussion of the determination of abundance of Hessian fly, Phytophaga 
destructor Say, is confined to methods used at the U. S. Entomological Field Station 
at West Lafayette, Indiana. Percentage and intensity of infestation are determined 
in the fall as an indication of the magnitude of the menace to fall sown wheat and 
the success of the advised control measures. A similar determination is made in the 
late spring to indicate the probable status of the Hessian fly menace to wheat sown 
the following fall. 
As vet no methods have been found acceptable for the determination either before 
or after harvest of the amount of damage done by Hessian fly. 
The use of so-called statistics in studies of this nature as well as in other entomologic¬ 
al investigations without appropriate consideration of the theory of probability is 
questioned. 
Most of the pioneer entomologists of this country must have felt 
the need of figures for the basis of opinions and consequently devised 
some sort of statistical methods for use in connection with their study 
of Hessian fly. Practically every economic entomologist since has 
contrived or adopted some scheme of measuring or estimating abundance 
of and damage by this most important insect pest of wheat. It is intended 
to confine the present discussion of methods of determination of 
abundance to those now used in making such determinations at the 
l Phytophaga destructor Say: family Cecidomyidae: order Diptera. 
