Last male wins the egg fertilization fight: A case study in ladybird, Menochilus sexmaculatus

Sexual maturity, lack of partner choice and sperm precedence in the promiscuous ladybird beetle Eriopis connexa (Germar): Who is my father?

Ladybird beetles present as key predator of many agricultural pests. Among them, Eriopis connexa stands out due some important traits for pest management programs such as common occurrence, population selected for resistance to pyrethroid insecticides, and possibility to be commercially available by rearing using alternative prey. Despite that, little is known about the role of polyandry and its effect on paternity in this species. Ladybird beetles engage in multiple matings, raising questions about the benefits of polyandry and paternity. We studied the selection of mating pair, sperm precedence, and offspring paternity by performing experiments on (1) the age of sexual maturity, (2) the frequency and refractory mating behavior within a photophase period, (3) the preference of insecticide-susceptible females to mate with either susceptible or resistant male phenotypes; and (4) the effect of multiple matings, on progeny paternity. Sexual maturity in E. connexa was found to begin within 3 days of adult emergence for both sexes, but fully developed after 5 days. The highest frequency of mating exhibited by sexual mature pairs occurred within first hour of pairing and the phenotype for insecticide resistance did not affect the choice of a mating partner. The resistance trait marker in the resistant beetle phenotype indicates that progeny paternity results from a mixture of available sperm and do not depend on mating order. These data suggest that released beetles would have a simple prospect for progeny production for both insecticide resistant and susceptible beetles.

Intergenerational fluctuations in colour morph frequencies may maintain elytral polymorphisms in the ladybird beetle Cheilomenes sexmaculata (Coleoptera: Coccinellidae)

Phenotypic polymorphisms are found in a wide array of taxa, and unravelling the mechanisms that maintain them is of great interest to evolutionary and ecological biologists. Temporal environmental heterogeneity may play a role in the maintenance of polymorphisms but is poorly understood. In the present study, we analysed trends in intergenerational elytral colour morph frequencies in relation to changes in fitness and life history traits (i.e. body size, mortality, fecundity, hatching rate and mate preference) in the ladybird beetle Cheilomenes sexmaculata (Coleoptera: Coccinellidae). A long-term field survey spanning nine years showed that the frequency of dark morphs increases over winter and then decreases in spring. Dark morphs may have an advantage in winter due to their higher tolerance of low temperatures compared with light morphs. Light-morph females were heavier in winter than dark-morph females. They also mated more frequently and had higher hatching rates, potentially causing an increase in light morphs in spring. These results suggest that fluctuations in morph frequencies resulting from the conflicting directions of selection pressures between overwintering and spring generations may help to maintain genetic polymorphism.

Mating system, age, and reproductive performance in Tenuisvalvae notata, a long-lived ladybird beetle

The long-lived polygynandrous ladybird beetle Tenuisvalvae notata (Mulsant) found in Brazil was evaluated in the laboratory for the effects of multiple mating and aging on its reproductive performance. This species is native to South America and is an important predator of mealybugs. Specifically studied were partner choice, female reproductive success, adult longevity, male virility, and offspring development. Young (5-10 days old) and older virgin females (95-100 days old) were subjected to either a single mate or multiple mating with the same or different males of various mating status (virgin or previously mated once, twice, and thrice). Results revealed a preference in both genders to mate with previously known partners. Additionally, younger females had higher fecundity and greater longevity when mated only once in comparison to those mated multiple times. Fecundity, fertility, and offspring development were similar across the treatments regardless of the number of mating or male mating history. Fecundity and fertility decreased throughout the oviposition period regardless of mating treatment.