COMPARISON OF ECDYSTEROID CONCENTRATION IN DIFFERENT MORPHS OF APHIDS

The amounts of ecdysteroids were determined in different morphs of hol ocyclic monoecious aphids (Acyrthosiphon pisum Harris, Dysaphis devect a Walk., Lachnus roboris L., Schizolachnus pineti F.) and holocyclic h eteroecious aphids (Aphis sambuci L., Rhopalosiphum padi L.) by means enzyme immunoassay. Among the parthenogenetic morphs (fundatrices, vir ginoparae, and oviparae), the fundatrices have consistently higher amo unts of ecdysteroids than those of other morphs of the same species. A late and apterous virginoparae showed slight differences in their ecdy steroid titer both in heteroecious and monoecious aphids. The migrant morphs (i.e., alate fundatrices and gynoparae) have the lowest amounts of ecdysteroids within a species. With the exception of D. devecta, t he oviparae of both heteroecious and monoecious aphids have the second greatest amounts of ecdysteroids among the morphs living on same host plant. Polyphenism, dispersal behavior, and fecundity In connection w ith weight, ovariole number, and ecdysteroid concentration of differen t morphs of aphids-are discussed. Copyright (C) 1996 Elsevier Science Inc.