464 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 9 



galls is quite uniform averaging about 3 mm. in length and 1 mm. in 

 diameter at the base. They are most abundant during the fall and 

 winter months. In many of the chrysanthemum growing districts 

 in the San Francisco Bay Region as much as one third of the crop is 

 annually lost unless preventive or control measures are adopted. Two 

 florists at Alameda who at one time grew large numbers of cut flowers 

 claim that the fly forced them out of business. Plants grown in green- 

 houses are injured most, but the attacks are also very severe in lath 

 houses. Plants growing out-of-doors in the average house garden do 

 not appear to become infested, at least a careful inspection has so far 

 failed to discover such, and infested plants taken from a greenhouse or 

 a lath house rapidly recover when placed outside where there is no 

 protection from the elements. Last August the writer secured twenty- 

 one infested plants from a greenhouse and set them in his garden. On 

 all of the new growth which has appeared to date (February 24) there 

 is not a single gall to be found, while checks left in the greenhouse and 

 removed to a lath house are either still badly infested or are entirely 

 ruined. It is perfectly possible however to conceive of a condition 

 outside in a particularly protected and warm place where the insect 

 may continue to breed. 



Distribution 



As previously stated the chrysanthemum gall-fly was first taken by 

 the writer in California at Berkeley, though investigations show that 

 it has been known to florists for over fifteen years in other places around 

 San Francisco Bay. The writer has taken it in Alameda, San Fran- 

 cisco and San Mateo Counties. It probably occurs in the other 

 counties which have not been visited. A single infested shoot of a 

 chrysanthemum was received last fall from Mr. Arthur E. Beers, 

 County Horticultural Commissioner, from Merced and it is not unlikely 

 that the insect is distributed throughout the state where chrysan- 

 themums are grown commercially. 



Food Plants 



The favorite food plant of this insect is the cultivated chrysan- 

 themum, some strains of which are more susceptible to attack than 

 others, but all appear to suffer to some extent at least. The ox-eye 

 daisy {Chrysanthemum leucanthemum) is listed as a host in Europe. ^ 



Control 



The practice of growing the bulk of the chrysanthemum crop under 

 cloth has been one of the chief means of preventing the attacks of the 



1 Kert6sz, C, Catalogus Dipterorum, II, p. 69, 1902. 



