190
N. WALOFF
regemteinensia (Danthanarayana, 1965) and A p - m immune (Williams,
1966). In both weevils the populations consisted of brachypterous forms
and of alate individuals which emigrated from the breeding sites.
Dispersal of the broom insects was memured with suction traps,
both the vent-axia and propeller type (Johnson, 1950; Taylor, 1951,
1955; Johnson and Taylor, 1965). The positions of two of the traps, one
at 1.2 m and the other at 9-1 m above ground level at distances of
100.6 m and 106.7 m S.S.W. of Area 4, remain fixed from year to year.
In one year a trap at ground level was also operated between these two,
and up to six suction traps have been used at various times.
The catches of broom insects were supplemented by broom trap
plants, planted on a logarithmic scale South of the plantation, and in
one year also at compass points radiating away from it. The small trap
plants were beaten daily and all the insects on them were collected
(Waloff and Bakker, 1963; Danthanarayana, 1965; Agwu, 1967). Immigration into the broom plantation was probably relatively unimportant
because there is no adjacent area of broom nearly rn big m our own plot.
Southwood (1960) in considering flight in Heteroptera aa a whole concluded that the family Miridae are the most active flyers in that order
of insects. We (Waloff and Bakker, Zoc. cit.) have studied flight in the
broom mirids and agree with Southwood (1962) that it can be distinguished into “flight” or dispersal outaide the breeding site and “flitting”
associated with feeding, mating, etc., within the habitat. “Flitting”
continued throughout the life of (L population, but flight tended to be
confined to the earlier half of ita life and wa8 undertaken mainly by
immature individuals.
Life of the adult populations of Miridae could usually be divided into
the preflight period lasting a week or more, the flight period extending
over several weeks and the poet flight period. The length of the flight
period was mainly determined by staggered emergence of the adults.
The proportion of the population that emigrated on any day depended on the physiological age of these Heteroptera and on weather,
mainly temperature. In 0. adenocczrpi and 0. vireaew the effect of age
and maturation is so great that it masks the effect of temperature which
steadily rises, as the populations are ageing.
The catches of the flying insecta by the suction traps, placed at different heights, and on the trap plants placed at different distances from
the plantation indicated that 0. Virescena and 0. concolot. have greater
powers of dispersal than the other three species.
Attempts were also made to estimate the proportions of the mirid
populations that emigrate, A graphical method was evolved (see Waloff
and Bakker, 1963) which basically is a comparison of the population
curve on time, with the curve denoting the magnitude of migratory
N. WALOFF
regemteinensia (Danthanarayana, 1965) and A p - m immune (Williams,
1966). In both weevils the populations consisted of brachypterous forms
and of alate individuals which emigrated from the breeding sites.
Dispersal of the broom insects was memured with suction traps,
both the vent-axia and propeller type (Johnson, 1950; Taylor, 1951,
1955; Johnson and Taylor, 1965). The positions of two of the traps, one
at 1.2 m and the other at 9-1 m above ground level at distances of
100.6 m and 106.7 m S.S.W. of Area 4, remain fixed from year to year.
In one year a trap at ground level was also operated between these two,
and up to six suction traps have been used at various times.
The catches of broom insects were supplemented by broom trap
plants, planted on a logarithmic scale South of the plantation, and in
one year also at compass points radiating away from it. The small trap
plants were beaten daily and all the insects on them were collected
(Waloff and Bakker, 1963; Danthanarayana, 1965; Agwu, 1967). Immigration into the broom plantation was probably relatively unimportant
because there is no adjacent area of broom nearly rn big m our own plot.
Southwood (1960) in considering flight in Heteroptera aa a whole concluded that the family Miridae are the most active flyers in that order
of insects. We (Waloff and Bakker, Zoc. cit.) have studied flight in the
broom mirids and agree with Southwood (1962) that it can be distinguished into “flight” or dispersal outaide the breeding site and “flitting”
associated with feeding, mating, etc., within the habitat. “Flitting”
continued throughout the life of (L population, but flight tended to be
confined to the earlier half of ita life and wa8 undertaken mainly by
immature individuals.
Life of the adult populations of Miridae could usually be divided into
the preflight period lasting a week or more, the flight period extending
over several weeks and the poet flight period. The length of the flight
period was mainly determined by staggered emergence of the adults.
The proportion of the population that emigrated on any day depended on the physiological age of these Heteroptera and on weather,
mainly temperature. In 0. adenocczrpi and 0. vireaew the effect of age
and maturation is so great that it masks the effect of temperature which
steadily rises, as the populations are ageing.
The catches of the flying insecta by the suction traps, placed at different heights, and on the trap plants placed at different distances from
the plantation indicated that 0. Virescena and 0. concolot. have greater
powers of dispersal than the other three species.
Attempts were also made to estimate the proportions of the mirid
populations that emigrate, A graphical method was evolved (see Waloff
and Bakker, 1963) which basically is a comparison of the population
curve on time, with the curve denoting the magnitude of migratory