Morphology and developmental plasticity of reproductive females in Myrmecina nipponica (Hymenoptera: Formicidae)

Abstract

We examined the morphology and developmental plasticity of alate/dealate queens and permanently wingless reproductive females (hereafter referred to as "intermorphic queens") in Myrmecina nipponica Wheeler. Alate/dealate queens and intermorphic queens had nearly equal reproductive capacities. The number of ovarioles was almost identical between virgin and inseminated alate/dealate queens, but inseminated intermorphic queens had significantly more ovarioles than virgin females. To determine if intermorphic queens in M. nipponica are 'ergatoid queens' or 'intercaste', we compared seven external traits of each female caste. The external traits of intermorphic queens, in particular pronotal width and Weber's length of the mesosoma, were more similar to workers than to alate/dealate queens. Data on ovarioles suggest that the intermorphic queens have a reproductive ability similar to alate/dealate queens. The absence of a reproductive female in a colony and low temperature stimulated the production of new intermorphic queens but not new alate queens. The plasticity afforded by the production of intermorphic queens is likely an adaptation to low food resources and patchy nest sites.