214 



Numerous parasites have been reared from Isosoma, the majority 

 of which are new. The most important parasites of /. iritici are 

 Ditroyinotus aureoviridis, Cwfd., and Homoporus chalcidojjhagus, 

 Walsh ; Eurytoma boUeri, Riley, var. parva, n., and E. pater, sp. n., are 

 also important ; the larva of the latter pierces the newly-formed gall 

 and places its egg on the Isosoma larva, completing its development 

 on the plant tissue after having consumed the host larva. The mite 

 Pediculoides ventricosus, Newp., is another active agent in the control 

 of /. iritici. 



One of the most promising control measures at present practised 

 is to plough under the wheat stubble as soon after harvest as possible, 

 and sow clover or grass in August or September. 



Dean (G. A.). Results of Ten Years of Experimental Wheat Sowing to 

 escape the Hessian Fly. — Jl. Econ. Entom., Concord, N.H., x, 

 no. 1, February 1917, pp. 146-162. 



Two of the most important factors to be considered by wheat 

 growers are the time of sowing to produce the maximum yield, and the 

 time for avoiding the Hessian fly [Mayetiola destructor]. Experimental 

 wheat sowings have led to the conclusion that the best time to secure a 

 maximum yield varies with the locality, the seasons and other con- 

 ditions. Tables are given showing the results of experimental sowings 

 in various localities of Kansas State : these results indicate that the 

 maximum yield would be obtained in an average season by sowing 

 a little earlier than the fly-free date. Sowing should be delayed 

 until as near the fly-free date as possible, as, if the Hessian fly is present 

 in damaging nmnbers and wheat is sown early, there is greater risk 

 of injury. Early ploughing of the stubble has been fomid very 

 effective in controlling the fly and also very successful in promoting 

 the growth of wheat in autumn, and thus permits a later sowing. 

 Late sowing, while preventing injury from the autumn brood of the 

 fly, is no protection against the main brood of the following spring, 

 which may migrate for several miles from an infested field or from 

 self-sown wheat or old stubble. Community codperation is the only 

 means of eliminating these dangers. 



McCoLLOCH (J. W.). Wind as a Factor in the Dispersion of the 

 Hessian Fly. — Jl. Econ. Entom., Concord, N.H. ,x,no. 1, February 

 1917, pp. 162-168. 



Experiments with wind screens have disclosed the fact that Hessian 

 fly [Mayetiola destructor] is undoubtedly dispersed by wind. The num- 

 ber of males caught in this fashion was practically negligible, but a large 

 number of females were taken which had apparently been fertilised 

 before flight, as they readily oviposited on wheat, all the eggs proving 

 fertile. These flies have been known to be carried over hills to the 

 uninf ested valleys on the other side. The fact that they were uninj ured 

 when caught on a screen at two miles distance from infested wheat 

 indicates that they could be carried much greater distances. In 

 Kansas State, the prevailing winds are from the south and south-west, 

 and it is noticeable that the spread of the fly has been slowest in a 

 south-westerly direction. A light wind is the most favourable to flight ; 



