INSECT ENEMIES AND THEIR CONTROL 121 
eggs deposited per day by an adult female white fly in a laboratory 
has been found to average very nearly four. Probably in the warmer 
temperature of a greenhouse this number is greater by one or two 
eggs per day. These observations, even though falling short of 
showing the normal increase in numbers of this species, emphasize 
the importance of a remedy which will, above all, destroy the adults 
and check at once the rapid deposition of eggs. A peculiarity of 
the egg-laying habits of this and some other species of white fly is 
the tendency to deposit the eggs in a circle while feeding, using the 
beak as a pivot. These circles, when completed, are about 144 mm. 
in diameter and usually contain’ from 10 to 20 eggs each. On the 
more hairy leaves groups of eggs of this kind are less frequently 
met with than on those which are more nearly smooth. The ma- 
jority of the adults are found upon the upper and newer leaves of 
the food plant. They are almost invariably found upon the under- 
side of the leaves, and it is here that nearly all the eggs are de- 
posited, although many are found upon the tender stems and leaf 
petioles and a very few scattering ones on the upper surfaces of 
the leaves. 
“The eggs are distinguishable with difficulty by the naked eye, 
being but one-fifth of a millimeter, or one one hundred and twenty- 
fifth of an inch, in length. They are more or less ovoid in form 
and suspended from the leaf by a short, slender stalk. With ordinary 
greenhouse temperatures the eggs hatch in from 10 to 12 days. The 
newly hatched insect is flat, oval in outline, and provided with ac- 
tive legs and antenne. It rarely crawls farther than one-half inch 
from the empty eggshell before settling down and inserting into the 
tissue of the leaf its threadlike beak. After feeding for five or six 
days, the insect is ready to molt its skin. The second and third 
stages are much alike, except in size, and differ principally from the 
first stage in that the legs and antenne are vestigial and apparently 
functionless. These two stages occupy from four to six days each. 
“The so-called pupal stage, up to the time when growth ceases, 
is in reality the fourth larval stage, the fourth larval skin envelop- 
ing the true pupa. The pupe and empty pupa skins are quite con- 
spicuous when the insects are abundant. Their outline is similar 
to that of the larve, but they are thicker and boxlike, about three- 
fourths of a millimeter, or three hundredths of an inch in length, 
and provided with long, slender wax rods or secretions which are 
