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    Resource allocations of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) in response to socio-sexual environment during immature and adult stages : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Entomology at Massey University, Palmerston North, New Zealand
    (Massey University, 2023) Liu, Junyan
    Animals adjust their investment in different life history traits according to their surroundings to maximise their fitness. Using a polygamous insect, the Mediterranean flour moth Ephestia kuehniella Zeller, which produces fertile eupyrene and infertile apyrene sperm, I investigated resource allocation strategies employed by males in response to socio-sexual cues during the adult and juvenile stages. I demonstrate that adult males raised their lifetime production and ejaculation of both eupyrenes and apyrenes after detecting either acoustic or chemical cues from adult rivals with combined cues strengthening such response, and that rival-experienced males could remember the sperm competition risk for most of their reproductive life. I manipulated juvenile socio-sexual settings and then examined their sperm production and ejaculation as well as survival, body and testis size, and mating behaviour. I provided the first evidence that juvenile social cues from conspecific larvae, pupae or adults had lasting impacts on lifetime sperm production and allocation. Adults from group-reared larvae, regardless of sex ratio, had smaller testes but produced more eupyrenes at emergence than from singly reared ones, and that body size and apyrene numbers remained the same across treatments. Male pupae had similar testis size but increased production of both eupyrenes and apyrenes at emergence in response to cues from conspecific pupae irrespective of sex. Late instar male larvae were able to detect cues from adult rivals and subsequently produced more sperm of both types at emergence, but adult cues had no effect on body and testis size. Juvenile socio-sexual environment had significant effects on sperm production and ejaculation during adult stage. My study indicates that after their late instar larvae were exposed to juvenile or adult rivals, adults produced and ejaculated more eupyrenes and apyrenes in their lifetime and had shorter mating latency. However, rival exposure had no effect on males’ mating frequency and longevity. Knowledge generated here enhances our understanding of how males of a polygamous insect calibrate their resource investment in response to dynamic social environment.
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    Plasticity in reproduction and survival under dynamic socio-sexual environment : empirical evidence from Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Entomology at Massey University, Palmerston North, New Zealand
    (Massey University, 2017) Esfandi, Kambiz
    Using an important pest of stored products, Ephestia kuehniella Zeller, I tested a number of theoretical predictions regarding strategies taken by males and females for resource allocations in response to dynamic socio-sexual environment. I demonstrate that males only respond to mean sperm competition levels and eupyrene sperm are produced both before and after emergence. Lifetime reproductive fitness in males depends on the number of copulations they can achieve, rather than the number of sperm ejaculated in each copulation. Regardless of whether males are exposed to rivals or not during their early adulthood, copulation duration and sperm allocation are not positively correlated, indicating that copulation duration cannot be used as a correct estimate of sperm allocation. Contrary to the previous prediction that males invest more in courting in the presence of rivals, my experiments demonstrate that males allocate more resource to courtship in the presence of additional females, which reduces their lifetime copulation frequency and fecundity. This finding offers a novel explanation for the success of mating disruption strategy using sex pheromones in pest management. Contradicting the previous prediction that females are more promiscuous under a female-biased condition and choosier in a male-biased sex ratio, my results show that perception of additional males makes females more receptive so that they mate more times and fertilise more eggs. Females call more when no additional mates or females are present than when either additional mates or females are present, suggesting that perception of no additional conspecifics by females may trigger them to allocate more energy for calling for further mating opportunities. Although virgin females lay similar numbers of eggs in all treatments, they start oviposition earlier and live shorter in the presence of conspecific males or females, supporting previous predictions that higher reproductive rate may accelerate senescence. Virgin females produce fewer eggs in male-biased than in female-biased sex ratio, suggesting that they reduce reproductive investment during their early life for mating opportunities under male-biased conditions. My studies provide insight into the plasticity in reproduction and survival under dynamic socio-sexual environment for animals with sexual reproduction in general and for this insect in particular.
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    Effect of nutrient limitation on the Mediterranean flour moth, Ephestia kuehniella Zeller : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Entomology at Massey University, Palmerston North, New Zealand
    (Massey University, 2016) Bhavanam, Santhi Priya
    The Mediterranean flour moth, Ephestia kuehniella is a cosmopolitan pest of stored products that now has wide distribution in flour/feed mills in New Zealand. Understanding how individual behaviour and life‐history strategies evolve in response to environmental variation will help predict the population dynamics and allow us to develop environmentally safe pest control measures. This study investigated effects of food shortage and the responses this stimulated in E. kuehniella. I artificially created food stress environment by rearing E. kuehniella larvae at five different population densities of 50, 100, 200, 400 & 800 on a constant amount of diet (50 g). Population density had a detrimental effect on E. kuehniella fitness. At higher population density (800) due to food shortage larval period was prolonged, percent survival and pupal mass of both sexes decreased. Poor nutrition during the larval stage also effected adult morphology and reproductive output. Female fecundity decreased with increased population density. Females that developed at high population density (800) emerged with small head, thorax and forewing, but food stressed females developed large abdomens relative to their body mass. There were no significant changes in female ovipositor length in response to nutrient limitation indicating that under poor environmental conditions females allocate more resources to reproduction and in particular to traits that influence offspring. In males, head and thorax width decreased with increased population density. Males at higher population density had large forewings relative to their body mass, possibly to aid movement to new habitats. Genital traits were insensitive to food shortage resulting from crowding. Although males at population densities of 400 & 800 produced fewer eupyrene sperm they had similar mating frequency and transferred similar numbers of apyrene sperm indicating that male development responds to juvenile environment. Males and females use visual and chemical cues to assess quality of potential mates during mate selection and prefer individuals that developed at high population density (800) compared to low population density (200) when their weights were matched, probably to obtain direct and indirect genetic benefits. Ephestia kuehniella obtains indirect genetic benefits through mate choice decisions. Body size has a heritable component and large parents produce large sons and daughters. Mother body mass influences offspring growth rate and daughter developmental period is shortened with increase in mother body mass but no such effect was observed on son developmental period indicating a nongenetic maternal effects. On the other hand, fathers do not have a notable influence on offspring growth rate and as a result the offspring of large fathers took longer to develop. Similarly, sons and daughters of polyandrous and cross culture females were heavier and polyandry increased female fitness especially in stressful conditions.
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    Reproductive behaviour of Ephestia Kuehniella Zeller (Lepidoptera: Pyradidae) : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Entomology at Massey University, Palmerston North, New Zealand
    (Massey University, 2010) Xu, Jin
    Ephestia kuehniella is a pest of stored grain products. It also is widely used to rear parasitoids and predators. Prior to this study, little information was available on its reproductive behaviour. The fitness of E. kuehniella decreases with the increase of rearing density; a density of 100 larvae/50g food is recommended to produce high quality insects. Females emerge earlier than males. Emergence peaks at dusk; calling, courtship and mating peak in the late part of the 1st scotophase following emergence; oviposition peaks in the early part of the 2nd scotophase following emergence. Newly emerged virgin females carry <5 mature eggs, and the egg load increase to ≈240 three days after emergence and remains unchanged thereafter. Male accessory gland secretions stimulate egg maturation; mated females produce ≈300 mature eggs. Males produce two types of sperm, eupyrene (nucleate) and apyrene (anucleate) sperm. After mating, it takes 11 h for most eupyrene and apyrene sperm to reach the spermatheca. The presence of eupyrene sperm in the spermatheca is the main factor that elicits oviposition. The highest fecundity can be achieved when both sexes are 1-d-old at mating compared to older insects; delaying mating for 7 d reduces female fecundity by 60%. There is no significant effect of parental age on offspring fitness. Virgin females live longer than mated ones because the former allocate less resource for egg production. Larger females have higher fecundity and larger males produce larger spermatophores. Larger parents have larger sons and daughters. Females prefer large and mid-aged males for mating. Males prefer large, young and virgin females for mating. Males strategically adjust ejaculate size according to the degree of sperm competition risks. Both sexes mate multiply where males can copulate up to 9 times and females up to 4 times in their lifetime. Larger and younger females are more likely to remate. Multiple mating does not increase female fecundity, fertility and longevity. Females discriminate against previous mates and strategically adjust oviposition to gain genetic benefit via increasing offspring genetic diversity. Using a chemosterilant, thiotepa, I determined that the last male to mate with a female sires most of her offspring. The last male sperm precedence may be due to sperm displacement at both sperm ejaculation and storage sites, where the 2nd male physically displaces the 1st male’s spermatophore with his own in the bursa copulatrix and triggers the female to dump ≈50% resident sperm in the spermatheca. Spermathecal contractions appear to be the mechanism for sperm ejection. The outcome of sperm displacement is the result of male×female interactions.