Endogenous periodicity in egg-number fluctuation in Lasius japonicus (Formicidae)

AbstractTo confirm oviposition periodicity in queen ants of Lasius japonicus (Formicidae), we performed breeding experiments under four constant conditions: 25, 20, and 17.5 °C under a 12L:12D photoperiod, and 17.5 °C under a 24L photoperiod. After nuptial flight, L. japonicus queens began to lay eggs immediately after the onset of breeding in all conditions. The number of eggs observed in each colony peaked on days 20–40 and then decreased gradually. After the decrease, the egg number began to increase and then decrease again in most colonies. Larval emergence occurred in some colonies but did not occur in many others. Period lengths of cyclic fluctuation in egg number, which were estimated using Fourier analysis, were on average 130–150 days in all four experimental conditions. Larval emergence seemed not to affect the peak days. The decline in queens’ oviposition activity might correspond with that occurring in nature.