REPORT OF THE STATE ENTOMOLOGIST I915 51 



CHRYSANTHEMUM MIDGE 

 Diarthronomyia kypogaea H.Lw. 



Specimens of badly infested chrysanthemum plants were received 

 under date of March 27, 191 5 from Prof. R. H. Pettit of the Michigan 

 Agricultural College, accompanied by the statement that this midge 

 was causing serious injury in the houses of a commercial chrysanthe- 

 mum grower at Adrian, Mich. A few plants accompanying this 

 communication were so badly swollen and distorted by the numerous 

 galls upon the leaves and stems that it was evident they could not 

 develop normally and were therefore practically valueless. This 

 was followed by the reception the latter part of September, of both 

 galls and adults from Arthur Gibson, first assistant government 

 entomologist, Department of Agriculture, Ottawa, Canada, and 

 from Prof. E. O. Essig, Berkeley, Cal., indicating that the species, 

 a European form, had become established in at least three widely 

 separated American localities. The pest has also been received 

 from Oregon. 



Injuries. The damage is caused by a small, reddish midge about 

 one-fifteenth of an inch long, which deposits its eggs upon the 

 developing plant, the type of damage depending largely upon the 

 time and manner of infestation. An abundant deposition of eggs 

 upon young plants 3 to 5 inches high may result in greatly enlarged, 

 irregularly swollen stems (these sometimes being twice their normal 

 diameter), deformed rudiments of leaves caused by an arrested 

 development, and a failure to produce blossoms, the plant making 

 an ill-shaped head. 



A less serious infestation, especially if this occurs after the plant 

 has secured a good start, may result in a few comparatively insig- 

 nificant swellings or galls on the stems, the presence of similar 

 growths, frequently rather scattered (plate 13) on the leaves and 

 more or less deformation of the flowers. Professor Pettit has found 

 the galls on leaves, stems, buds and calyxes, though no plants coming 

 into our hands have borne affected flowers. 



Food plants. This insect has been recorded from central and 

 southern Europe as infesting Chrysanthemum leucan- 

 themum, C. corymbosum, C. atratum, C. japoni- 

 c u m and C. myconis, the first named, at least, being deformed 

 as seriously and as variously as described above for the cultivated 

 chrysanthemum in this country. It was first noticed in America 

 on the variety known as mistletoe. Most cultivated chrysanthe- 

 mums appear to be susceptible though, owing to the apparently 

 local habits of the midges, the infestation is apt to be very uneven. 



