196
N. WALOFF
this type however are the pod beetle Bmhidius ater (Parnell, 1966) and
the shield bug Piemhrw.9 litwdue (Javahery, 1967). The hibernation
sites of Bruchidius are widely scattered away from broom and the
greatest change in the numbers of the adult population of this species
result from dispersal to the hibernation sites. To give an example, of
the one million adults that emerged from pods in Area 4 in 1960, only
68 000 or 7 yo aggregated in the plantation in the following spripg. Thus
enormous fractions of adult populations disperse from their breeding
sites and emigration by flight is a widespread attribute of insect populations. When carried to an extreme, aa in locusta (Rdney, 1963;
Waloff, 1966) or in the frit fly (Southwood, 1965) whole, or nearly whole
populations may be on the move, but more generally fractions of populations w i l l remain in the original breeding sites. Some species are polymorphic and produce migratory forms, such aa the alatae in aphids and
the macropterous form of Lsitona regenateinensie, but most insects set
aside part of their adult life to migratory flight to which they are temporarily physiologically attuned. This hse been repeatedly pointed out
by Kennedy (1961) and by Johnson, but what may be st&
here is
the importance of this activity to that fraction of the population that
remains in the original breeding site and from which the danger of
potential overcrowding is temporarily allevhted. At various times the
populations of psyllida, Leumpteru and the combined populations of
mirids were enormous and the habitat waa heavily exploited, but the
stress was temporarily relaxed after the dispersal of populations of
these insects.
X. FINAL CONSIDERATIONS
Probably there are few strictly monophagous species, but those that
live and breed on a host plant, such as broom, are on closer terms with
one another than those which inhabit some more diffuse habitat. The
studies on the broom fauna have provided good evidence that many of
the species have significant effects on one another’s abundance. Some
actually feed on one another, others by e.cting &B alternate sources of
food for predators, or more rarely aa alternate hoete for paraaites, act as
protective agencies. The fauna on broom is large and aome of the species
abundant. In any area of broomland, the complex interactions do not
affect all the members of the fauna to the same degree and the assembly
of species with its millions of psyllids, aphids, moths and mirids in their
peak years resembles a galaxy with a number of closer constellations
within it. Moreover, the phytophagous species cannot be considered in
the abstract without their host plant, with which they interact. For
this reason, the term the “life system” proposed by Geier (1965) and
developed by Clark et d. (1987) is more embracing than a “community”
N. WALOFF
this type however are the pod beetle Bmhidius ater (Parnell, 1966) and
the shield bug Piemhrw.9 litwdue (Javahery, 1967). The hibernation
sites of Bruchidius are widely scattered away from broom and the
greatest change in the numbers of the adult population of this species
result from dispersal to the hibernation sites. To give an example, of
the one million adults that emerged from pods in Area 4 in 1960, only
68 000 or 7 yo aggregated in the plantation in the following spripg. Thus
enormous fractions of adult populations disperse from their breeding
sites and emigration by flight is a widespread attribute of insect populations. When carried to an extreme, aa in locusta (Rdney, 1963;
Waloff, 1966) or in the frit fly (Southwood, 1965) whole, or nearly whole
populations may be on the move, but more generally fractions of populations w i l l remain in the original breeding sites. Some species are polymorphic and produce migratory forms, such aa the alatae in aphids and
the macropterous form of Lsitona regenateinensie, but most insects set
aside part of their adult life to migratory flight to which they are temporarily physiologically attuned. This hse been repeatedly pointed out
by Kennedy (1961) and by Johnson, but what may be st&
here is
the importance of this activity to that fraction of the population that
remains in the original breeding site and from which the danger of
potential overcrowding is temporarily allevhted. At various times the
populations of psyllida, Leumpteru and the combined populations of
mirids were enormous and the habitat waa heavily exploited, but the
stress was temporarily relaxed after the dispersal of populations of
these insects.
X. FINAL CONSIDERATIONS
Probably there are few strictly monophagous species, but those that
live and breed on a host plant, such as broom, are on closer terms with
one another than those which inhabit some more diffuse habitat. The
studies on the broom fauna have provided good evidence that many of
the species have significant effects on one another’s abundance. Some
actually feed on one another, others by e.cting &B alternate sources of
food for predators, or more rarely aa alternate hoete for paraaites, act as
protective agencies. The fauna on broom is large and aome of the species
abundant. In any area of broomland, the complex interactions do not
affect all the members of the fauna to the same degree and the assembly
of species with its millions of psyllids, aphids, moths and mirids in their
peak years resembles a galaxy with a number of closer constellations
within it. Moreover, the phytophagous species cannot be considered in
the abstract without their host plant, with which they interact. For
this reason, the term the “life system” proposed by Geier (1965) and
developed by Clark et d. (1987) is more embracing than a “community”