Effects of population density on alienicolae of Aphis fabae Scop.: The expression of migratory urge among alatae in the field

SUMMARY Alate Aphis fabae from field infestations on beans and sugar beet were tested for flight before parturition and divided into migrants, flyers and non‐flyers. More alatae were produced, fewer nymphs were deposited before flight and the proportions of migrants among alatae increased with population density on each of the three crops. After the population peak, proportions of migrants decreased, more interforms were produced and more nymphs were deposited before flight.