20 
BULLETIN 746, U. S. DEPARTMENT OE AGRICULTURE. 
and another egg is deposited, part of it extending over a portion 
of the surface of the first egg. More eggs are deposited in the same 
way, the female gradually moving downward and backward, so that 
she stands over the slowly enlarging cluster. As the eggs overlap, 
one being deposited partly over the other, the completed cluster 
more than ever resembles a group of fish scales (see PL II). 
In this action the moth is very quiet, her wings folded, antennae 
back, and legs apart. She keeps the tip of her ovipositor pressed 
against the leaf continuously, making it difficult for an observer to 
ascertain the exact time any one egg is deposited. During the action 
she raises the body "on tiptoe," relaxing and resting against the 
leaf at intervals. One cluster of 6 eggs was formed in 16^ minutes, 
and another moth laid 
34 es^s in 8 minutes. 
Oviposition is be- 
gun at dusk and con- 
tinues throughout the 
night, the female fly- 
ing and walking occa- 
sionally. Many clus- 
ters of different num- 
bers of eggs may be 
formed in the same 
night. Individuals 
deposit eggs during 
one, two, three, or 
four nights, never 
longer. Oviposition 
is extended over several nights in cooler weather. Males in the same 
cage with egg-laying females are indifferent, paying no attention to 
their mates. 
EGG. 
' jr & r <f» 
"^"*»»» 
\ 
b 
X 
po 
Fig. 6. — Diagram showing relationship of mean tempera- 
ture to length of egg period of the sugar-cane moth 
borer, and indicating line of calculated means. 
dots represent period means of individuals. 
The 
DURATION OF THE EGG STAGE. 
The duration of the egg stage has been found to be from 4 to 9 
days, depending on the temperature, with the average for the year 
a trifle over 5 days. These results have been obtained from experi- 
ments in the insectary, but it is probable that greater variations 
between the minhnum and the maximum periods occur in the field. 
The period of incubation has been lengthened to 12 days by placing 
the eggs in an ice box and it is likely that they will stand even 
greater retardation without being killed. The temperature in the 
ice box was not very low and eggs laid in the early spring or late 
fall would probably require as long to hatch. The average length 
