12
1 0
I -
j 0.1
5
z
M. E. SOLOMON
-
-
oe%
O O ~
Ponolis
/. 00
. Ellopio
Eupithecia
Thera
-
Semiothiso
\------/ Bupolus
1
1
1
,
,
,
,
,
,
,
I
1950
1952
1954
1956
1958
1960
FIG. 5. Population density of phytophagous caterpillars in a forest of Scots pine. (From
Klomp, 1962.) The horizontal line has been added to indicate Klomp’s estimated mean
density for Bupalus.
figures of Varley and Gradwell (above) is rather close, in spite of the
great differences between pine and oak.
Another set of data for Lepidoptera feeding on pine foliage was
published by Schwerdtfeger (1935, 1941). These were based on censuses
of overwintering pupae or larvae on the ground in forests at Letzlinger
Heide, Germany. They were conveniently re-graphed on a logarithmic
scale by Varley (1949) ; I have read off approximate values of the ranges
of fluctuation on this logarithmic scale and converted them to a geometric scale. Two of the species were among those dealt with by Klomp
(loc. cit.), namely the Noctuid Panolis griseovariegata (Goeze) and the
Geometrid Bupalus piniarius (L.) - the pine beauty and the bordered
white. A third species, the pine hawk, Hyloicus (or Sphinx) pinastri (L.)
was also dealt with by both authors, but Klomp’s data were too incomplete for the present purpose. A fourth species studied by Schwerdtfeger was the Lasiocampid Dendrolimus pini L. The graphs show marked
fluctuations of all four species, rather irregular but with a tendency to
oscillations of 7 or 8 years duration (9 or 10 years in the case of Hyloicus).
Some of the peaks in these fluctuations represent severe outbreaks.
Normally, one should take account of these facts in selecting the length
of the periods in which to measure the ranges of fluctuation, but I have
simply started at the beginning of the records and used successive
10-year periods for comparison with the other examples. The figures
cover the period 1881-1940, except the last 10 years for Hyloicus.
1 0
I -
j 0.1
5
z
M. E. SOLOMON
-
-
oe%
O O ~
Ponolis
/. 00
. Ellopio
Eupithecia
Thera
-
Semiothiso
\------/ Bupolus
1
1
1
,
,
,
,
,
,
,
I
1950
1952
1954
1956
1958
1960
FIG. 5. Population density of phytophagous caterpillars in a forest of Scots pine. (From
Klomp, 1962.) The horizontal line has been added to indicate Klomp’s estimated mean
density for Bupalus.
figures of Varley and Gradwell (above) is rather close, in spite of the
great differences between pine and oak.
Another set of data for Lepidoptera feeding on pine foliage was
published by Schwerdtfeger (1935, 1941). These were based on censuses
of overwintering pupae or larvae on the ground in forests at Letzlinger
Heide, Germany. They were conveniently re-graphed on a logarithmic
scale by Varley (1949) ; I have read off approximate values of the ranges
of fluctuation on this logarithmic scale and converted them to a geometric scale. Two of the species were among those dealt with by Klomp
(loc. cit.), namely the Noctuid Panolis griseovariegata (Goeze) and the
Geometrid Bupalus piniarius (L.) - the pine beauty and the bordered
white. A third species, the pine hawk, Hyloicus (or Sphinx) pinastri (L.)
was also dealt with by both authors, but Klomp’s data were too incomplete for the present purpose. A fourth species studied by Schwerdtfeger was the Lasiocampid Dendrolimus pini L. The graphs show marked
fluctuations of all four species, rather irregular but with a tendency to
oscillations of 7 or 8 years duration (9 or 10 years in the case of Hyloicus).
Some of the peaks in these fluctuations represent severe outbreaks.
Normally, one should take account of these facts in selecting the length
of the periods in which to measure the ranges of fluctuation, but I have
simply started at the beginning of the records and used successive
10-year periods for comparison with the other examples. The figures
cover the period 1881-1940, except the last 10 years for Hyloicus.