Development and reproduction of two color forms of english grain aphid (Homoptera: Aphididae)

Abstract

The life cycle of apterous and alate viviparae of pink and green color forms of the English grain aphid, Sitobion avenae (F.), were compared at 20 ± 1°C and a photoperiod of 14:10 (L:D) h, using individually caged aphids that were examined daily on 'Clintland 64' oat, Avena sativa L. Two studies were conducted, using 22 replicates with apterous and alate S. avenae, and 132 replicates with only apterous forms. Alate aphids had a greater prereproductive period than apterous aphids, probably in part because their metabolism was directed towards wing development before reproduction. Apterous pink aphids had a shorter reproductive period than all other forms. This, together with their higher intrinsic rate of increase (r(in)), may represent an advantage over green aphids for colony growth, although this advantage may be reduced because alate pink aphids had the smallest r(in) of the aphid forms. Alate aphids tended to have a longer postreproductive period. The longevity of apterous pink aph