130 
gate and often whitish in color, undergo a more complete meta¬ 
morphosis, and when mature emerge as very minute winged in¬ 
sects, usually pale yellow in color. 
Scale insects obtain their food as do the plant-lice; that is, 
they insert their beaks into the plant tissue and live on the plant 
juices. When abundant they soon exhaust the life of the plant. 
Treatment .—Probably the most effective treatment against 
scale insects in greenhouses is spraying with whale-oil soap, used 
at the rate of one pound of the soap to a gallon of warm water. 
At this strength the more resistant plants, such as palms and 
Ficus, will not be injured, but for ferns this remedy is un¬ 
safe. Fir-tree oil, altho more expensive and hardly as effective 
as whale-oil soap, is useful against scales On ferns, orchids, and 
the more tender plants generally, when applied at a rate of about 
i part to 20 parts of water. The plants should be thoroly sprayed 
with water three or four hours after applying either of the above 
contact insecticides. 
Some of the scales may be removed with water by using a 
strong pressure, but most of them are too firmly attached for the 
successful use of this method unless they are first loosened with a 
stiff brush. After using the water spray it is advisable to apply 
one of the insecticides just mentioned, in order to destroy any 
scales which may not have been dislodged by the stream of water. 
The Greenhouse White Fey 
Aleyrodes vaporariorum Westw. 
One of the commonest and most troublesome insects which the 
florist must fight is the white fly. Its original home is probably 
the tropical or subtropical countries, but at present it is found 
generally distributed over Europe and the United States, altho in 
northern Illinois it is a pest only in greenhouses. It is a very 
general feeder and can live on most greenhouse plants, but is not 
injurious to all that it infests. We have found Salvia, Coleus , 
Fuchsia, Geranium „ Pelargonium, Ageratum, Begonia , celestial 
peppers, and tropical Solanums particularly susceptible to its at¬ 
tacks. It obtains its foods by sucking out the sap as do plant-lice 
and scale insects. 
The winged adult (Fig. 48) is about 3/50 of an inch in length, 
and looks as if it had been dusted with flour—which accounts 
for its popular name. The minute, irregularly ovoid, yellowish 
green eggs are deposited on the under surface of the leaves, to 
which each is attached by a very short, slender peduncle, or stem. 
Recently hatched larv?e are flat, oval in outline, and transparent 
or translucent according to age. They settle upon the leaf in the 
