49 



lar sluqws, .such as arc ^shown in the illustration (Plate III), having 

 somewhat the senil)lanee of a gall, which name has l)ecn rather generally 

 applied to them ])y florists. After the formation of the "gall," what 

 is known as wet I'ot is apt to set in and destroy the leaves. This 

 has the ultimate etieet of dwarfing the plants and of arresting the 

 development of the tiowor buds. 



From the frequency with which maggots resem])ling those found on 

 the leaves of violets are found in the soil in violet houses, it has been 

 thought that the insects live both in the soil and upon the leaves. It 

 has been thought, also, that this pest is more apt to make its appearance 

 in greenhouses where proper attention lias not been paid to the mixing 

 of the soil and to drainage, and that manures of some kinds favor its 

 development. It seems probal)lo, however, in the light of more tech- 

 nical knowledge of the subject that the larvai found in soil are in nearly 

 every case those of Mycetophilida?, and probabh^ of difi'erent species of 

 Sciara, several forms of which occur in greenhouses, of which some are 

 reported to l)e injurious while some are scavengers. One of these spe- 

 cies known as the tickle midge will l)e treated farther on in the present 

 publication. 



LITERATURE OF THE SPECIES. 



What appears to be the lirst account that can be with positiveness 

 attributed to this species of "gall tly" was published in the Florists' 

 Exchange (Dec. 19, 1896, p. 1132), by Mr. Dorsett. At that time it 

 was not known that this species was different from the so-called gall 

 flies of roses. The account in question is a short one, and is illustrated 

 by a half-tone reproduction of a photograph showing injury to violet 

 leaves ))y the larva'. In the same publication (issue of December 3, 

 1898), Mr. W. Davison wrote of the occurrence of this species at 

 Nyack, N. Y., and in The American Florist for January 21, 1899, Dr. 

 L. O. Howard gave a brief summary of what was then known concern- 

 ing the insect. In Mr. Galloway's " Commercial Violet Culture," pub- 

 lished the same year, this species is considered on pages 211-214, inju- 

 ries by the larvae to the flowers of violet being illustrated. 



The aim of the present article is to present in concise, summarized 

 form most of the facts Avhich have already been made public in the 

 articles above quoted. 



REMEDIES. 



Hydrocyanic acid gas does not appear to have been tested against 

 the violet gall fly, or if it has been used we have no published account 

 of the fact. There is no reason to believe that it would be less effective 

 than when employed against aphides and other insects. Its use is, 

 therefore, suggested. It does not seem practical to pick the leaves, 

 because in such cases the crowns are permanently injured and flower- 

 ing is checked. Mr. Galloway suggests the use of air-slaked lime, 

 19288— No. 27--()l 4 



