60 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. ‘he 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 4o 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 
