132 
Sometimes the dropping of the lower leaves is indicative of their 
presence. The larvae and pupae secrete a honeydew, which falls 
on the upper surface of the leaves below them, and on badly in¬ 
fested plants, where this sweetish liquid becomes abundant, a 
sooty fungous growth appears on the surface of the leaves cov¬ 
ered with the honeydew, and this growth hastens the death of 
the plants. 
Natural Enemies .—In the university greenhouse, at Urbana, 
many of the plants, especially Salvia and pansy geranium, were 
badly infested with the white fly, but a month or so later they 
were almost completely freed from it, owing to the appearance 
of a minute hymenopterous parasite which multiplied so fast that 
the white fly was unable to hold its own. This parasite proved 
to be a new species, and has recently been described by Mr. A. 
A. Girault as Encarsia versicolor * It attacks the immature forms 
of the white fly, and parasitized young may be recognized by their 
black appearance, those not parasitized being pale greenish. 
We have also found the ladybirds very beneficial in destroy¬ 
ing larvae and pupae of the white fly. 
Remedies .—Fumigation with hydrocyanic acid gas is by far 
the most efficient known means of controlling this pest in green¬ 
houses. In moderately tight houses it may be used, for an all- 
night fumigation, at a strength of i ounce of cyanide of potassium 
to 3500 cubic feet of space. It is necessary to fumigate three or 
four times at intervals of about ten davs to two weeks. 
The materials necessary for fumigation with hydrocyanic acid 
gas are potassium cyanide (98 to 99 percent pure), commercial 
sulphuric acid, and water; and the utensils required are half¬ 
gallon or gallon stone, earthen, or granite jars, and a supply of 
ordinary small paper bags. 
*Encarsia versicolor species novum, a Eulophid Parasite of the Green¬ 
house Whiteflv, Alcyrodcs vaporariorum Westwood. Psyche, Vol. XV, No. 
3 (June, 1908), pp. 53 - 57 - Cambridge, Mass. 
