April, ’24] 
larrimer: hessian fly statistics 
203 
U. S. Entomological Field Station at West Lafayette, Indiana and to 
express an opinion as to the general unreliability of methods of deter¬ 
mination of amount of damage. 
Abundance 
The abundance of Hesssian fly is determined twice each year, once 
in the fall and again late in the spring, each time for a different purpose. 
Both determinations are made by the same method and at the time 
when most of the fly forms of the respective generations are in the 
flaxseed stage. 
Regular date of sowing experiments distributed over the area under 
observation but entirely at random as far as Hessian fly infestation 
is concerned, serve as the source of material. These experiments con¬ 
sist of five to seven sowings of approximately one-tenth acre each, made 
at intervals of three to five days before and after a date previously 
considered as the best sowing date. A sample of wheat plants is taken 
from each sowing by a method which is an adjustment of the various 
theoretical and practical demands. In this case it consists of approxi¬ 
mately one hundred plants taken in five random lots of approximately 
twenty plants or culms each. The samples thus obtained are removed 
to the laboratory where they are carefully examined and the following 
information is recorded; number and respective date of sowings; 
number of plants and number of culms examined; percent of plants 
and percent of culms infested; for the fly forms that are larvae, the 
size, total number and maximum and average number per infested 
culm; and for the fly forms that are puparia, the total number and the 
maximum and average number per infested culm. 
Flaxseeds obtained from the fall examination are caged in 9x36mm. 
glass vials plugged with cotton and inserted in holes bored in plaster 
slabs to rear possible parasites for specific determination. No attempt 
is made to determine the percentage of parasitism in the fall because 
the presence or absence of parasites at this time does not directly 
affect any possible artifical control measures as yet developed and does 
not assist in the formulation of a program of action to meet a possible 
spring menace of Hessian fly. 
The principal results therefore of the fall examination are the deter¬ 
mination for each experiment of the percentage and intensity of in¬ 
festation of the samples from the sowings made on different dates and 
the determination and distribution of the parasites obtained. The 
