Preference and plasticity in selection of host for oviposition in Black Marsh Dart Onychargia atrocyana Selys, 1865 (Odonata: Zygoptera: Platycnemididae)

An experimental study was conducted in a natural pond to investigate host plant preference and plasticity in damselfly Onychargia atrocyana. The hypothesis was that this species has a host preference for oviposition and also sufficient plasticity to use other hosts in the absence of the preferred host. After mating, tandems were observed landing on plants in search of suitable oviposition substrates. The majority of landings occurred on Alternanthera philoxeroides, followed by Colocasia esculenta and Commelina diffusa. The frequency of landings on A. philoxeroides and C. esculenta was not significantly different, while landings on C. esculenta and C. diffusa did differ significantly. In the absence of emergent littoral plants, the damselflies exhibited plasticity in host preference and shifted ovipositional substrate by laying eggs on submerged areas of petioles of free-floating Eichhornia crassipes. Females of O. atrocyana exhibited a flexible oviposition strategy, transitioning from a combination of emergent and submerged oviposition to primarily selecting emergent oviposition in most cases. Additionally, they divided oviposition events into multiple phases when required to ensure successful reproduction. E. crassipes supported a higher rate of oviposition compared to other plants. A multiple regression analysis demonstrated that during submerged oviposition water temperature and pH were significant predictors of the duration of submergence.