D Y N A M I C S OF FIELD P O P U L A T I O N O F P I N E LOOPER
303
Consequently, genotypes iminuiie for mutua 1 interference are not
stimulated to disperse, and being a t a disadvantage will be selected
against, notwithstanding the higher survival rates they have in other
respects. This suggests that the functional significance of the mutual
interference among larvae a t densities well below the immediate capacity of the food plant would be the dispersal of the individuals of one
batch. The dispersal will only be effective, howevor, when the larvae can
move to areas not yet occupied by the individua‘ls of other egg batches,
i.e. when the density is not too high. It is therefore striking that the
mechanism of dispersal seems to be so close1;y bound up with the
mechanism regulating population density.
ACKNOWLEDGMENTS
My thanks are due in the first place to my assietants Mr. J. Kleinhout
and Mr. B. J. Teerink, for their great help in the daily routines of the
time-consuming ecological field work, for their -willingness to visit the
rather isolated study area a t quite “abnormal” moments of the day on
bicycle or motorcycle in spite of wind, rain, or snowfall, and last but not
least for their warm interest in the biological probleme we tried to solve
in excellent co-operation.
Further, I wish to express my sincere gratitude to the late Prof. L.
Tinbergen and to Dr. A . D. VoQte, who raised my interest in the ecological problems of insect populations, and to Ir. J. H. van Tuil,
Director of “Het Nationale Park De Hoge Veluvre”, who permitted me
to work in the pine woods of the park.
Finally, my thanks are due to Yeveral students and to the personnel
of the National Park who helped me in more than one respect, and to
Dr. M. R. Honer for correcting the English text.
REFERENCES
Balch, R. E. and Bird, F. T. (1944). Scient. Agric. 25, 65-80. A diseaae of the
European spruce sawfly, Gilpinia hercyniae (Htg.).
Brereton, J. Le Gay (1962). In “The Evolution of L.ving Organisms” (G. W.
Leeper, ed.), pp. 81-93. Evolved regulatory mechanisms of population control. Melbourne University Press.
Brower, L. P. (1958). Am. Nat. 92, 183-187. Bird predation and foodplmt
specificity i n closely related procryptic insects.
Chitty, D. (1955). In “The Numbers of Man and Animals” (J. B. Cragg and
N. W. Pirie, eds.), pp. 57-67. Adverse effects of population density upon the
viability of later generations. Edinburgh: Oliver and Boyd.
Chitty, D. (1957). Cold Spring Harbor Symp. Quant. Biol. 22, 277-280. Selfregulation of numbers through changes i n viability.
Escherich, K. (1931). “Die Forstinsekten Mitteleuropas”, Bd, 111. Berlin: Paul
Parey Verlag.
Gruys, P. (1963). “Annual Report 1962 of the Inst. Bid. Field Res.”, Arnhem.
303
Consequently, genotypes iminuiie for mutua 1 interference are not
stimulated to disperse, and being a t a disadvantage will be selected
against, notwithstanding the higher survival rates they have in other
respects. This suggests that the functional significance of the mutual
interference among larvae a t densities well below the immediate capacity of the food plant would be the dispersal of the individuals of one
batch. The dispersal will only be effective, howevor, when the larvae can
move to areas not yet occupied by the individua‘ls of other egg batches,
i.e. when the density is not too high. It is therefore striking that the
mechanism of dispersal seems to be so close1;y bound up with the
mechanism regulating population density.
ACKNOWLEDGMENTS
My thanks are due in the first place to my assietants Mr. J. Kleinhout
and Mr. B. J. Teerink, for their great help in the daily routines of the
time-consuming ecological field work, for their -willingness to visit the
rather isolated study area a t quite “abnormal” moments of the day on
bicycle or motorcycle in spite of wind, rain, or snowfall, and last but not
least for their warm interest in the biological probleme we tried to solve
in excellent co-operation.
Further, I wish to express my sincere gratitude to the late Prof. L.
Tinbergen and to Dr. A . D. VoQte, who raised my interest in the ecological problems of insect populations, and to Ir. J. H. van Tuil,
Director of “Het Nationale Park De Hoge Veluvre”, who permitted me
to work in the pine woods of the park.
Finally, my thanks are due to Yeveral students and to the personnel
of the National Park who helped me in more than one respect, and to
Dr. M. R. Honer for correcting the English text.
REFERENCES
Balch, R. E. and Bird, F. T. (1944). Scient. Agric. 25, 65-80. A diseaae of the
European spruce sawfly, Gilpinia hercyniae (Htg.).
Brereton, J. Le Gay (1962). In “The Evolution of L.ving Organisms” (G. W.
Leeper, ed.), pp. 81-93. Evolved regulatory mechanisms of population control. Melbourne University Press.
Brower, L. P. (1958). Am. Nat. 92, 183-187. Bird predation and foodplmt
specificity i n closely related procryptic insects.
Chitty, D. (1955). In “The Numbers of Man and Animals” (J. B. Cragg and
N. W. Pirie, eds.), pp. 57-67. Adverse effects of population density upon the
viability of later generations. Edinburgh: Oliver and Boyd.
Chitty, D. (1957). Cold Spring Harbor Symp. Quant. Biol. 22, 277-280. Selfregulation of numbers through changes i n viability.
Escherich, K. (1931). “Die Forstinsekten Mitteleuropas”, Bd, 111. Berlin: Paul
Parey Verlag.
Gruys, P. (1963). “Annual Report 1962 of the Inst. Bid. Field Res.”, Arnhem.