DYNAMICS O F FIELD POPULATION O F P I X E LOOPER
255
able to show that maximum egg diameter is highly correlated with egg weight,
showing that diameter at any rate can be used as an indel for weight or volume.
The mean egg diameters of individual females have been plotted over
fecundity in Fig. 15 within the pupal diameter c1a:ises 4.6-5.0, for the
year 1963. Graphs for the extreme pupal size classes have not been composed because of the low numbers within these classes (see Fig. 14,
bottom graph). Figure 15 shows that in two out of five pupal classes egg
size decreases significantly with an increasing fecundity; in two other
cases (pupae 4.6 and 5.0) the evidence strongly suggests such a decrease;
only in one case (pupa 4.9 mm) there is no indication of declining
egg size, but as appears from Fig. 14 the fecund females fail in this
series. In other years the conformable relationships are very similar to
those of 1963.
All the evidence together proves that within cne pupal size-class
fecundity and egg size are correlated. This is diagrammatically illustrated by graph A of Fig. 16. It can be derived from this diagram, that
addition of the graphs shown in Fig. 15 must result in an overall negative correla6ion between fecundity and mean egg diameter. This is
shown for 1963 in Fig. 17.
The regression coefficient of the relation shown in Fig. 17 amounts to -0.0058,
and deviates significantly from zero (P = 0.025). Similar calculations have been
performed for the years 1954, 1955, 1957 and 1958 and the regression coefficients
were respectively -0*0008(43), -0.0019(66), -0.0030('74) and -0.0028(27)
(number of females studied in brackets), which deviate from zero in the year
1957 (P = 0.05) only.
For all years that such an overall regression coefficient of mean egg
size on fecundity has been computed, its value is smaller than may be
expected from the corresponding relationships within one pupal size
class (cf. Fig. 15 with Fig. 17). This is because the egg size increases with
an increase of pupal diameter. This is diagrammatmally illustrated in
Fig. l&B, and the actual data for 1963 are shown :m Fig. 18.
The regression coefficient of the relation shown in Fig. 18 amounts to 0.422,
but does not deviate significantly from zero (P = 0.22). I n other years the
corresponding coefficients are positive as well, and amount to 0.953( 1954),
0-389(1955), 0-571(1957), 0*882( 1958), and 0*502(1959). Tke fact that all values
computed are positive makes it very probable that the egg diameter increases
with an increase of pupal diameter. Under the hypothesif that no relationship
exists there is an equal chance for getting positivb and negative values. The
probability of having six equal values then amounts to 2 x (1/2)O = 0.03. Moreover, the regression coefficient deviates significantly from zero in the year 1954
(P = 0.007).
As already shown in the paragraphs on pupal size (p. 252) part of the
variability of the pupae is genetic. It is logical to assume that an
255
able to show that maximum egg diameter is highly correlated with egg weight,
showing that diameter at any rate can be used as an indel for weight or volume.
The mean egg diameters of individual females have been plotted over
fecundity in Fig. 15 within the pupal diameter c1a:ises 4.6-5.0, for the
year 1963. Graphs for the extreme pupal size classes have not been composed because of the low numbers within these classes (see Fig. 14,
bottom graph). Figure 15 shows that in two out of five pupal classes egg
size decreases significantly with an increasing fecundity; in two other
cases (pupae 4.6 and 5.0) the evidence strongly suggests such a decrease;
only in one case (pupa 4.9 mm) there is no indication of declining
egg size, but as appears from Fig. 14 the fecund females fail in this
series. In other years the conformable relationships are very similar to
those of 1963.
All the evidence together proves that within cne pupal size-class
fecundity and egg size are correlated. This is diagrammatically illustrated by graph A of Fig. 16. It can be derived from this diagram, that
addition of the graphs shown in Fig. 15 must result in an overall negative correla6ion between fecundity and mean egg diameter. This is
shown for 1963 in Fig. 17.
The regression coefficient of the relation shown in Fig. 17 amounts to -0.0058,
and deviates significantly from zero (P = 0.025). Similar calculations have been
performed for the years 1954, 1955, 1957 and 1958 and the regression coefficients
were respectively -0*0008(43), -0.0019(66), -0.0030('74) and -0.0028(27)
(number of females studied in brackets), which deviate from zero in the year
1957 (P = 0.05) only.
For all years that such an overall regression coefficient of mean egg
size on fecundity has been computed, its value is smaller than may be
expected from the corresponding relationships within one pupal size
class (cf. Fig. 15 with Fig. 17). This is because the egg size increases with
an increase of pupal diameter. This is diagrammatmally illustrated in
Fig. l&B, and the actual data for 1963 are shown :m Fig. 18.
The regression coefficient of the relation shown in Fig. 18 amounts to 0.422,
but does not deviate significantly from zero (P = 0.22). I n other years the
corresponding coefficients are positive as well, and amount to 0.953( 1954),
0-389(1955), 0-571(1957), 0*882( 1958), and 0*502(1959). Tke fact that all values
computed are positive makes it very probable that the egg diameter increases
with an increase of pupal diameter. Under the hypothesif that no relationship
exists there is an equal chance for getting positivb and negative values. The
probability of having six equal values then amounts to 2 x (1/2)O = 0.03. Moreover, the regression coefficient deviates significantly from zero in the year 1954
(P = 0.007).
As already shown in the paragraphs on pupal size (p. 252) part of the
variability of the pupae is genetic. It is logical to assume that an