58 
Fig. 56.— Head of plant- 
louse, showing suck- 
ing beak — much, en- 
larged (original, Divi 
sion of Entomology). 
PLANT-LICE. 
Several forms of plant-lice affect the leaves of sugar beet, but as far 
as at present known do not inflict extensive injury. Among the plant- 
lice, however, are some few forms which have the habit of feeding on 
the roots, being known as root-lice, and these are of the greatest 
importance when atmospheric conditions conduce 
to their development or the plants are first injured 
through other causes. 
THE MELON PL.ANT-LOTTSE. 
{Aphis gossypii Glov. ) 
The melon plant-louse or, as it is more commonly 
known, the melon louse, is perhaps the commonest 
species found on beets, and is the best known as 
well as most destructive of all insects of this class. 
Fortunately for the beet grower it does not favor 
this crop, and is usually found onty in moderate 
numbers on beets when other plants are available. 
The writer has seen a considerable number of this species on beet 
leaves working in their usual manner by pumping up the juices 
through their beaks (fig. 56), but although the plants were carefully 
watched the operations of the plant-lice did not seem to hinder the 
growth of the plants in any degree. Nevertheless, this louse is capa- 
ble of serious damage, more especialh^ in the event of exhaustion of 
favorite host plants, like melons and 
other cucurbits, which would drive it 
to beets if these were most available. 
The principal forms of this insect are 
illustrated in figure 57. 
The melon louse is probabl}' of 
American origin and perhaps tropical, 
since it prefers plants of a tropical 
nature, has a very wide distribution 
in North and South America and the 
West Indies, and has been observed in 
Australia. It is therefore apt to be 
present in most fields of sugar beet, 
but its occurrence there can usualh^ be 
traced to other plants on which it develops more freely, some of which 
have alread}^ been mentioned. Among others of the favorite host 
plants are cotton, okra, purslane, strawberry, and orauge and other 
citrus trees. Attack begins in earl}^ spring and may last until winter, 
according to season, climate, and other circumstances. 
Natural enemies. — As an illustration of an insect pest held in abey- 
FiG. 57. — ApMs gossypii: a, winged female; 
aa, enlarged antenna of same; ah, dark 
female, side view; h, young nymph or 
larva; c, last stage of njrmph; d, wingless 
female — all greatly enlarged (original, 
Division of Entomology) . 
