6o NEW YORK STATE MUSEUM 



therefrom is very probably an equal amount. A number of green- 

 houses were visited in October 1906, and several of them showed 

 serious injury as a result of the work of this pest. The crop, 

 according to estimates of growers, is reduced in many houses from 

 one third to one half, involving a considerable loss in the aggregate, 

 and should this infestation become more general, the results may be 

 very serious to the industry as a whole. 



An examination showed that the insect was distinctly local in 

 its operations, since one half of a house 150 feet long might be 

 seriously injured, while the other half was almost exempt from at- 

 tack. Even in smaller houses there were distinct areas which suffered 

 more severely than others, sometimes these being limited to only 

 a square yard or two. The larvae at the time of our investigation 

 had mostly disappeared, though in the Rockefeller house they were 

 rather abundant. This is probably to be explained by the fact that 

 the proprietors have allowed the temperature of their houses to 

 remain rather high in the last few weeks, hoping to enable the 

 plants in a measure to outgrow the injury earlier inflicted. The 

 growers are almost unanimous in stating that when the temperature 

 of a house can be kept down to 40 at night, not rising over 60 in 

 the daytime, there is very little or no injury from this pest, and 

 examination of other houses where this low temperature had been 

 maintained, bore out their statements. The flies, according to the 

 growers, very rarely leave the plants and can be discovered only 

 by flushing them with the hand. An examination showed, even in 

 houses where there were flies on the plants and numerous larvae, 

 that none were to be found on the windows, even in the sheds at 

 the ends of the houses nor in cobwebs spun here and there about 

 the structure. The insect displays a marked preference for recently 

 opened leaves, apparently depositing its eggs in those which have 

 just expanded fully and, according to the growers, leaves perfectly 

 straight one day may be badly curled the next. They note that 

 leaves can be curled in a few hours and are of the opinion that 

 only a day or so lapses between the deposit of the egg and the 

 curling of the leaves, an operation which protects the larva from 

 most insecticides. Furthermore, several of them state that fumiga- 

 tion with hydrocyanic acid gas apparently has no influence whatso- 

 ever in destroying the larvae, though there is little doubt but that 

 the flies are killed. There is a marked periodicity in the abundance 

 of the larvae. Last summer they were first noticed in numbers 

 early in July and then they became abundant again in August, and 

 experience this year has shown that they may continue working in 



