I
1950/51
1952/!S
1954/55
l95Ej/5?
1958/59 ' 1960/6(
l Q & / . S
' 1961;/65
GENERATIONS (YEARS)
FIQ. 27. Fluctuations of density over 15 years of various stages of the pine looper.
Densities connected by solid lines refer to independent field estimates; those connected by
the broken line (larvae I) are indirect estimates, obtained from the product of egg densities
and annual egg survival rates. Larval density (September) in 1962-63 was not measured
directly (see Tables IV and XXIII).
I
,
4961
1963
1955
105?
1959
f961
I963
GENERATIONS
(YEARS)
FIQ. 28. Changes in pupal density in April over 14 years, indicated by the shifts of the
95% confidence intervals presented in Table VIII. See the text.