206 : ALEYRODES. 
Tobacco decoction, or tobacco used as a finely ground pow- 
der, also has good effect. In greenhouses tobacco is the standard 
remedy, and repeated application is almost certain to keep the 
plants free of the pest. It is usually burnt, the smoke pene- 
trating everywhere among the foliage, killing the insects. Fre- 
gently the steam pipes are simply covered with moist tobacco 
stems to produce the atmosphere poisonous to the lice. 
In forcing beds, the lice can be killed by placing shallow 
dishes of carbon bisulphide in them, which are left over night 
in the covered beds. The poisonous fumes of this liquid are 
very effective, and can also be used in greenhouses. In this case 
the plants, and dish, are covered with a box for two or three 
hours, or a fumigating box can be used, in which a number of 
potted plants, infested with lice, are exposed to the fumes. In 
every greenhouse and nursery such fumigation boxes should be 
found, for they are useful in many ways. As far as bisulphide 
of carbon is concerned, it should be handled with care, and always 
away from fire. The fumes do not rise, but being five times 
heavier than air, they sink down, hence the box should be quite 
tight. One dram of liquid per cubic foot of space is sufficient, 
and this quantity will not injure the vegetation, but will kill all 
the lice by the time it has evaporated. 
The enemies of plant-lice will be considered later. 
If we wish to eat fruit, if we wish to harvest crops of all 
kinds, we have to observe closely and nip the evil in the bud, 
i. e. destroy. the destructive bugs as soon as they make their 
appearance. 
FAMILY ALEYROIDAE. 
(Aleyrodes). 
The insects are like scale insects in their immature stage, 
and for a long time were classed with them, but the mature 
insects differ so much from the Coccidz or Scale Insects, that 
now they are classified as a distinct family. They are very small 
insects, and both sexes are winged. In the adult stage all species 
are similar in color, having white wings, sometimes spotted, with 
a yellowish or pinkish body, more or less spotted with black. 
The adults of both sexes have the wings and body covered with 
a whitish powder, which has given them the name aleurodes, 
i. e. like flour. 
