54 NEW YORK STATE MUSEUM 



that this latter, as in the case of the allied rose midge and Hessian 

 fly, may be completed in four weeks or less. 



Observations in a commercial greenhouse show that the insects 

 are comparatively inactive during the winter when temperatures 

 are kept low (about 50 degrees), but as the houses warm up in the 

 spring the pests become more active and a serious infestation may 

 prevail for a time. This seems to be followed by a quiescent period 

 which probably persists through the summer and then there is a 

 resumption of activities in the fall, since rather badly infested plants 

 and emerging flies were again to be found about the middle of October. 

 Plants growing outdoors appear to be relatively free from infestation. 



Distribution and future probabilities. This species has been 

 recorded from central and southern Europe and, as stated above, 

 it has already become established in several widely separated locali- 

 ties in this country, probably by the shipment of infested plants or 

 cuttings. It was very likely brought to America without the normal 

 quota of parasites and for a time at least it may prove to be a some- 

 what difficult insect to control, though it would seem as if the native 

 parasites of our large and varied gall midge fauna might in time 

 prey most successfully upon this midge. 



g| Control measures. It is desirable to ascertain the present distri- 

 bution of the chrysanthemum midge in America, and growers of this 

 popular flower would do well to adopt every reasonable precaution 

 to keep their stock free from the insect, especially since it lives also 

 upon the common white daisy, Chrysanthemum leu- 

 canthemum, a widely distributed, introduced weed which would 

 probably mean the persistence of the insect in a locality once it 

 becomes well established, with presumably more or less perennial 

 infestation and injury to cultivated chrysanthemums. 



Badly infested plants should be burned (they are practically 

 worthless) and it is possible that by cutting off and destroying the 

 infested portions of others, it may be practical to exterminate the 

 insect in greenhouses without resorting to -more drastic measures. 

 Fumigation with hydrocyanic acid gas has been practised by one 

 large grower with considerable success, and so long as this treat- 

 ment was given nightly the infestation was comparatively light, 

 though if for any reason it was impossible to fumigate, midges were 

 likely to be numerous the next day. Data at hand incline us to 

 believe that this treatment can hardly be considered as more than 

 repressive, and on that account we would emphasize the desirability 

 of starting with clean stock and adopting every reasonable means 

 to avoid infestation. 



