47 



cle entitled •'Conibatini,^ Aphis on Violets," published b}' Mr. Gallo- 

 way in American Garden inj»- for November 6, 1897 (Vol. XVIII, 

 p. 758), from which the followinj>- is quoted: 



Aphides, especially the blark ones, were once the most serious i)ests with which we 

 had to contend. Since we have adopted the hydrocyanic-acid gas treatment, how- 

 ever, * * * we have had no serious trouble. So imi)ortant do we consider this 

 matter of being able to use this gas that we shall plant in the future throughout the 

 entire season in such a way that the plants may be fumigated at any time. 



"We abandoned tobaci'o entirely some time ago, as we found by experience that, 

 no matter how used, it would tend to weaken tlie foliage and make it UKjre subject 

 not only to "six)t," but to other diseases as well. * * * When tobacco is used, 

 either as smoke, dust, stems, or extract, it seems to in a measure check the vital 

 tunctions of the leaf, the little cells of which temporarily lose their vitality and 

 their ability to resist outside influences. Here is the opportunity the fungus needs, 

 and it at once takes advantage of it by sending a thin, thread-like growth into tlie 

 cells. Once the tissue is entered, the fungus continues to grow until the \>\-dnt is 

 able to check it of its own accord. The spot then turns white, but when I'onditions 

 are again favorable the fungus will start anew, and the spot will l)e found soft, 

 greenish, and watery, etc. 



THE VIOLET "GALL FLY." 



[Diplosis riolirola C'oq.) 



Violets and roses are subject to the attack of dift'erent forms of 

 minute larva? or maggots, the 3^oung of what are known to Horists as 

 gall flies — minute two-winged flies or gnats of the family Cecidomyiidai. 

 Three species are of importance as enemies of these plants, and there 

 are doubtless others, but these three are the ordy ones that have 

 obtained marked recognition by their injuries in recent years; until 

 recentl}^ indeed, they were not recognized as distinct from others of 

 their kind. They have been given more or less study 1)V the writer 

 and l)y some others, and, when it was made manifest that they were 

 undescribed through special study by Mr. D. W. Coquillett, of this 

 office, all of the notes and manuscripts which had accumulated at that 

 time were turned over to him, and the results were embodied in two 

 somewhat technical articles, with full descriptions, in Bulletin No. 22 

 of the present series. 



DESCRIPTION. 



The larva or maggot, which is usually found folded up in the leaf 

 of a violet in such a manner as to bring the upper surfaces together in 

 what has been termed a gall, is a minute, legless creature of a whitish 

 or yellowish color. The general appearance of one of these larvae is 

 shown in figure 10 at d, e representing its breastbone. 



The parent gall fly is a minute, slender and delicate two-winged fly, 

 measuring about one-twentieth of an inch in length. It has long and 

 slender legs and antennte, the latter 1-1-jointed and surrounded by two 

 whorls of bristly hairs on joints 3 to 13, inclusive. 



