REPORT OF THE STATE ENTOMOLOGIST I912 39 



there must be a sufficient period for the completion of a Hfe cycle 

 before another brood of flies can appear, and if at that time and 

 for a considerable j)eriod thereafter the weather be hot and dry, 

 comparatively few or no flies will appear till conditions change. 



We know that early sown wheat is very apt to become badly 

 infested in the fall, while late sown grain frequently escapes. In 

 the first instance the young wheat is in a succulent condition and 

 receives a deposition of eggs before or between killing frosts, while 

 in the other case it escapes. If the flies emerge early and there is 

 no gram available, the most of the insects perish and the infesta- 

 tion is very slight or negligible. Weather conditions must always 

 be considered in sowing winter wheat. The general rule may be 

 staied as follows : Moist, warm weather in early fall will permit 

 the safe sowing of wheat at a relatively early date, but when the 

 fall is dry delay sowing till the latest possible date. The normal 

 or average date when wheat can be sown in New York without 

 danger of its becoming infested with Hessian fly is about Sep- 

 tember 20th. 



Parasites. The parasites of the Hessian fly are of much value 

 in controlling this pest. The easiest way to determine the parasitism 

 in a field is to take infested stalks and rear the insects. A net- 

 covered jelly tumbler or fruit jar, taking care to avoid close covers 

 and the resulting molds, will answer very well as a breeding cage. 

 An examination of the '' flaxseeds " late in the season after the 

 parasites have emerged under natural conditions will give some idea 

 of the relative numbers which have been killed by these beneficial 

 insects. Sometimes fully 90 per cent are destroyed by parasites, 

 and occasionally entomologists have experienced difficulty in obtain- 

 ing midges from infested wheat because parasites were so abundant. 



A representative sample of infested wheat was taken from the 

 field of Mr F. C. Walker, of Byron, and the insects reared. It was 

 found that 119 puparia were parasitized, 11 diseased and 37 in a 

 normal condition. In other words, 70 per cent of the " flaxseeds " 

 were parasitized, 8 per cent diseased and less than 12 per cent were 

 in a condition to produce flies. The two most abundant parasites 

 were Merisus destructor Say and Tetrastich us 

 carinatus Forbes, numerous samples of both being reared. 

 In addition, one specimen of Eupelmus allyni French, a 

 species of Tetrastichus, one of Callimone, one of Pleurotropis and 

 a Pteromalid were obtained. These determinations were made by 

 Mr J. C. Crawford through the courtesy of Dr L. O. Howard and 



