30 BULLETIN 885, TJ. S. DEPARTMENT OF AGRICULTURE. 
eggs, there is a rest of from 30 seconds to several minutes before op- 
position is resumed and the female sometimes wanders around with 
wings fluttering, especially when observed. Since the distance which 
the female moves forward is variable and since she may be disturbed 
by other individuals on the leaf or by obstacles such as pupa cases 
or scale insects, the egg mass is often far from being a spiral. The 
figures show two masses. Molino and Dietz have observed 15 and 17 
eggs laid in 15 minutes and likewise have seen as few as 3 eggs laid in 
10 minutes. 
In the field it has been observed that on bright sunshiny days the 
eggs are laid in the morning before noon, or in the late afternoon, 
times at which the relative humidity is highest. On cloudy days, 
when the relative humidity is fairly constant, egg laying may take 
place at any time during the day. 
Normally, the eggs are laid on the undersides of the leaves, the 
females being negatively phototropic at the time of oviposition as is 
shown by the fact that when leaves on which females are laying eggs 
are turned over oviposition invariably soon ceases. In many cases 
a female will lay eggs within a few millimeters of the pupa case from 
which she has emerged. Likewise females seem to show little judg- 
ment as to where they lay eggs, this often resulting in decided over- 
crowding of young growth with eggs and the subsequent death of 
large numbers of developing individuals. Attention has been called 
to this under the heading "Spread of the insect," page 12. On a 
young orange on September 9, 1918, 50 spirals were counted on a 
single leaf and the following numbers were counted : 500 eggs in an 
area 10 by 30 mm. and 800 eggs in an area 20 by 25 mm. On Sep- 
tember 30 there were at least 3,500 eggs on each leaf. 
Some writers have called attention to the fact that eggs are laid on 
the fruit, and Morrison succeeded in getting a female in captivity to 
lay a normal spiral on a lemon fruit. Numerous inspections of lime, 
orange, and tangerine fruits on well-infested trees have failed to show 
that oviposition on the fruit in the field is a normal thing, for no stages 
of the black fly except occasional adults have ever been found on such 
fruit. Out of ten attempts, using 750 mixed adults brought in on 
young growth where they had clustered and confining them on half- 
ripe lime fruits, only one spiral of 19 eggs was obtained whereas a 
number of freshly laid spirals were found even on wilted leaves. 
Hence, it may be assumed that only on certain occasions and under 
certain conditions will eggs be found on the fruit of infested trees. 
This will probably be when the fruit is well shaded and the tree very 
heavily infested. 
The number of eggs in a spiral or "mass" is as subject to variation 
as is the shape of the "masses" themselves and varies from 7 to 81, 
these being the extremes. Out of 118 spirals consisting of 3,798 eggs 
