, Volume 31, Issue 2, pp 153–158

Why do males emerge before females?

A hypothesis to explain the incidence of protandry in butterflies


  • Christer Wiklund
    • Department of ZoologyUniversity of Stockholm
  • Torbjörn Fagerström
    • Swedish Coniferous Forest Project

DOI: 10.1007/BF00346917

Cite this article as:
Wiklund, C. & Fagerström, T. Oecologia (1977) 31: 153. doi:10.1007/BF00346917


In butterflies and many other insects there is a general tendency for males to emerge before females. This is known as protandry. In this paper we advance the hypothesis that protandry is a reproductive strategy of males, resulting from competition for mates, and should primarily occur in species maintaining female monogamy. Our hypothesis is corroborated by applying a mathematical treatment to a theoretical population with seven defined properties, all of which are argued to be reasonable assumptions for natural populations.

Copyright information

© Springer-Verlag 1977