340
H . KLOMP
may have influenced the occurrence of disease. This does not apply to
deaths caused by parasites and those results have been used for further
analysis of the population dynamics (p. 267).
c. R E A R I N G O F PUPAE
As reported on p. 226, pupal density was assessed in April of each
year by searching through 24 m2 of litter which yielded 15 to 120 pupae.
Such numbers are too low to provide a reliable estimation of the pupal
mortality rate and therefore further pupae were collected by searching
less accurately through litter lying outside the sampling squares and on
localities scattered throughout the study area. By this means some
hundreds of pupae were collected and reared in 0.37 litre glass jars containing a small amount of litter with not more than seven pupae per jar.
The sexes were separated and grouped into classes of 0.1 mm pupal
diameter (for reasons see later). The breeding results are given in
Table XV. Pupae which putrefied have been deducted from the original
numbers. In 1963, of 418 pupae 12 putrefied (see Fig. l2), thus 406
pupae were reared and are shown in Table XV. The percentage parasitism represents an unbiased estimate of pupal infection in April because no parasites leave their hosts before the middle of May. However,
the adults of Cratichneumon nigritarius, which emerge and fly in the
second half of May, infect pupae of the pine looper which have still to
emerge. Consequently, the ultimate pupal mortality due to parasites
will be higher than indicated in Table XV. We have no data bearing on
the increase of the percentage parasitism, but it is probably low in most
years since the parasite is rare.
Both mortality from putrefaction and furtker infestation by the
ichneumon can be assessed indirectly (see p. 272). All other parasites
infect host larvae. For more details on their ecological significance
see p. 294.
D. REARINQ O F MOTHS
Moths have been reared in great numbers in most years to measure
adult fecundity. (See next chapter for results.)
IV. ANNUAL VARIATIONS OF THE REPRODUCTIVE RATE
The mean fecundity of the moths expressed as mean number of eggs
deposited, showed significant variations year to year. These variations
have been analysed and will now be described. First we shall consider
variability of fecundity within one generation, then secondly, the
annual changes in fecundity.
H . KLOMP
may have influenced the occurrence of disease. This does not apply to
deaths caused by parasites and those results have been used for further
analysis of the population dynamics (p. 267).
c. R E A R I N G O F PUPAE
As reported on p. 226, pupal density was assessed in April of each
year by searching through 24 m2 of litter which yielded 15 to 120 pupae.
Such numbers are too low to provide a reliable estimation of the pupal
mortality rate and therefore further pupae were collected by searching
less accurately through litter lying outside the sampling squares and on
localities scattered throughout the study area. By this means some
hundreds of pupae were collected and reared in 0.37 litre glass jars containing a small amount of litter with not more than seven pupae per jar.
The sexes were separated and grouped into classes of 0.1 mm pupal
diameter (for reasons see later). The breeding results are given in
Table XV. Pupae which putrefied have been deducted from the original
numbers. In 1963, of 418 pupae 12 putrefied (see Fig. l2), thus 406
pupae were reared and are shown in Table XV. The percentage parasitism represents an unbiased estimate of pupal infection in April because no parasites leave their hosts before the middle of May. However,
the adults of Cratichneumon nigritarius, which emerge and fly in the
second half of May, infect pupae of the pine looper which have still to
emerge. Consequently, the ultimate pupal mortality due to parasites
will be higher than indicated in Table XV. We have no data bearing on
the increase of the percentage parasitism, but it is probably low in most
years since the parasite is rare.
Both mortality from putrefaction and furtker infestation by the
ichneumon can be assessed indirectly (see p. 272). All other parasites
infect host larvae. For more details on their ecological significance
see p. 294.
D. REARINQ O F MOTHS
Moths have been reared in great numbers in most years to measure
adult fecundity. (See next chapter for results.)
IV. ANNUAL VARIATIONS OF THE REPRODUCTIVE RATE
The mean fecundity of the moths expressed as mean number of eggs
deposited, showed significant variations year to year. These variations
have been analysed and will now be described. First we shall consider
variability of fecundity within one generation, then secondly, the
annual changes in fecundity.