Epitoky in Scutisotoma stepposa (Collembola; Isotomidae)

Abstract

Reproductive males of Scutisotoma stepposa Martynova from two basins of Vitim Plateau (Russia: East Siberia) display epitoky in three forms. ‘Supermales’ are armed with strong macrosetae, brushes on ventrum of abdomen, callosities on tube and legs, bent and thickened antennae. ‘Modest’ males have only strong macrosetae and slightly thickened antennae. ‘Neutral’ males are indistinguishable from females. In the Vitim Plateau, the species often forms mass aggregations. Population sizes of S. stepposa are usually depressed during the first half of the summer and increase as of August. The reproductive individuals occur during the entire vegetative season, and all three types of males can occur together. ‘Neutral’ males are more frequent under low population densities, while ‘supermales’ are seen only in aggregations. Taxonomic remarks and new records of S. stepposa from the Palearctic are given.

Keywords

• Polymorphism
• aggregations
• sexual dimorphism
• life cycle
• swarm