Triangular fecundity function and ageing in ladybird beetles

Abstract

Abstract. 1. In insects, the age schedules of fecundity tend to be triangular and this has been attributed more to temporal patterns of mortality than to fecundity. The objective of the work reported here was to test the assumption that senescence shapes the fecundity function in ladybird beetles, and in particular that the production function declines with age.2. The results of a laboratory study on three species of predatory ladybird beetle indicated that the efficiency with which these insects acquire and process food declined with age. Although supplied with the same amount of food each day, after the onset of reproduction, these beetles ate less and less with increasing age. Egg production mirrored the decline in aphid consumption. Associated with this was a decline in fertility, assimilation, and speed of locomotion with age.3. This study indicates that production declined with age and that this shaped the fecundity schedules in these ladybird beetles. In addition, the results indicated that ladybirds are income breeders and, as predicted, the reproductive effort of the small species was greater than that of the large species used in this study.

Reproductive diapause in Hippodamia convergens (Coleoptera: Coccinellidae) and its life history consequences

“…This distribution of reproductive effort is consistent with the triangular fecundity 13 function inferred by Dixon and Agarwala (2002) for coccinellid females, reflecting 14 a maximal reproductive effort shortly after onset of reproduction that declined 15 gradually with age. Similarly, ovipositing females on the maintenance diet 16 required four days to effectively convert animal protein into eggs (Fig.…”

On the assessment of prey suitability in aphidophagous Coccinellidae

“…Providing C. transversalis is representative, the shortest pre-oviposition period, the longest oviposition period, and the longest lifespan will all tend to be obtained on the same diet that yields the highest per capita production of viable eggs. Since fecundity declines quite steeply with adult age (Dixon & Agarwala, 2002), measurements of the quantity and fertility of eggs produced by a series of females over a fixed period in early adult life is likely sufficient to assess relative prey suitability for adults. Estimates of total lifetime reproductive success are of interest in theoretical models of fitness, but they are not requisite for assessment of diet suitability.…”

Ladybird Coccinella septempunctata (Coleoptera: Coccinellidae) prefers toxic prey in laboratory choice experiment

“…We used postdiapause, preoviposition adults to minimize variability in feeding rate. Although supplied with the same amount of food, reproducing ladybirds gradually decreased their feeding rate with increasing age (Dixon & Agarwala, 2002).…”