Aphids (Homoptera: Aphidoidea) produce a number of different phenotypes in
their life-cycle, among which are winged (alate) and wingless (apterous) mo
rphs. Lowe & Taylor (1964) and Sutherland (1969a, b) were the first to sugg
est that aphid clones differ in their propensity to produce the winged morp
h and that in the pea aphid (Acyrthosiphon pisum Harris), this propensity i
s linked to the colour of the phenotype. We tested for the occurrence of ge
netic variation in winged morph production by rearing individuals from red
and green clones of pea aphid under wing-inducing (crowding) and control co
nditions, and scored the phenotypes of their offspring. Clones differed sig
nificantly in alate production and red clones produced on average a higher
proportion of winged morphs than green clones. Importantly, however, there
was considerable variation between clones of the same colour. Broad-sense h
eritabilities of winged morph production were 0.69 (crowding treatment) and
0.63 (control). Clones also differed in the number of offspring they produ
ced. When exposed to the crowding stimulus, aphids deferred offspring produ
ction, resulting in a higher number of offspring produced in the crowding t
reatment than in the control.