Lifetime egg production of captive libellulids (Odonata)


The estimation of lifetime egg production (LEP) is a central question in ecology, since the number of eggs produced determines the potential size of the following generation. In this study, I tried to obtain a rough estimation of the LEPs in libellulids in outdoor cages. The main questions were: (1) does hand feeding influence females’ life history traits; (2) how long is the maturation period and the lifespan; (3) does the quality/quantity of eggs vary with female age or size; and (4) how many eggs do females lay in their lifetime? I installed two outdoor cages and kept individually marked specimens of Orthetrum coerulescens and Sympetrum striolatum under semi-natural circumstances. Orthetrum coerulescens had a longer life span in hand-fed specimens compared to not hand-fed. The maturation period, number of clutches, clutch size, egg circumference, and LEP did not differ between hand-fed and not hand-fed specimens. The median maturation period was shorter in O. coerulescens (24 days hand-fed; 20 days not hand-fed) than in S. striolatum (47 days, all hand-fed). The mortality during the maturation period was high in both studied species (O. coerulescens 81.48%, S. striolatum 89.16%). Orthetrum coerulescens had a shorter median life span than S. striolatum. The quality/quantity of eggs did not correlate with females’ age and size. Orthetrum coerulescens had a mean calculated lifetime egg production of 3081 eggs per specimen and S. striolatum 1041 eggs per specimen. The data pertain to outdoor cage experiments (a reduced spectrum of prey, no long flights possible, no predators present). Nevertheless, they may provide a very rough estimation of LEP for two libellulid species.

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