Aphids exhibit a polymorphism whereby individual aphids are either winged o
r unwinged. The winged dispersal morph is mainly responsible for the coloni
zation of new plants and, in many species, is produced in response to adver
se environmental conditions. Aphids are attacked by a wide range of special
ized predators and predation has been shown to strongly influence the growt
h and persistence of aphid colonies. In two experiments, we reared two clon
es of pea aphid (Acyrthosiphon pisum) in the presence and absence of predat
ory ladybirds (Coccinella septempunctata or Adalia bipunctata). In both exp
eriments, the presence of a predator enhanced the proportion of winged morp
hs among the offspring produced by the aphids. The aphid clones differed in
their reaction to the presence of a ladybird, suggesting the presence of g
enetic variation for this trait. A treatment that simulated disturbance cau
sed by predators did not enhance winged offspring production. The experimen
ts indicate that aphids respond to the presence of a predator by producing
the dispersal morph which can escape by flight to colonize other plants. In
contrast to previous examples of predator-induced defence this shift in pr
ey morphology does not lead to better protection against predator attack, b
ut enables aphids to leave plants when mortality risks are high.