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Beneficial insects, such as natural enemies, are important to agro‐ecosystem functioning and thus agricultural production. Parasitoids and predators can provide sustainable long‐term solutions to pest problems (biological control), reducing the need for expensive and sometimes polluting pesticide applications. When several species of beneficial insects are present, their pest control actions may be additive, synergistic, or disruptive. One form of disruptive interaction between parasitoids and predators is direct interspecific contest for access to individual pests (the resource to be exploited). This study evaluated behavioural interactions between brood‐guarding wasps, Goniozus nephantidis (Muesebeck) (Hymenoptera: Bethylidae), which are known to engage in intra‐specific contests, and a predatory bug, Cardiastethus exiguus (Poppius) (Hemiptera: Anthocoridae), which attack the same pest species, Opisina arenosella (Walker) (Lepidoptera: Oecophoridae), a major pest in coconut production systems. Dyadic parasitoid–predator and predator–predator contests were staged to determine the factors that influence the behaviours within, and outcomes of, such interactions. Parasitoids were aggressive towards predators, sometimes killing them, but predators were not aggressive towards parasitoids. Biting and stinging only occurred when there was a host larva present. In the absence of the parasitoid that had oviposited onto a host, predators often consumed the parasitoid's eggs. Egg consumption sometimes occurred when the parasitoid was present. Intra‐specific competition between pairs of predators was also evaluated: adults were aggressive towards each other, but interactions were not fatal. Biting was more common when there was no prey larva present. When a larva was present, predators were observed feeding simultaneously. We conclude that direct parasitoid–predator interactions are likely to influence pest population dynamics, possibly reducing the overall suppression of O. arenosella by its natural enemies. [ABSTRACT FROM AUTHOR]

Kinship among interacting individuals is often associated with sociality and also with sex ratio effects. Parasitoids in the bethylid genus Goniozus are sub‐social, with single foundress females exhibiting post‐ovipositional maternal care via short‐term aggressive host and brood defence against conspecific females. Due to local mate competition (LMC) and broods normally being produced by a single foundress, sex ratios are female‐biased. Contests between adult females are, however, not normally fatal, and aggression is reduced when competing females are kin, raising the possibility of multi‐foundress reproduction on some hosts. Here, we screen for further life‐history effects of kinship by varying the numbers and relatedness of foundresses confined together with a host resource and also by varying the size of host. We confined groups of 1–8 Goniozus nephantidis females together with a host for 5+ days. Multi‐foundress groups were either all siblings or all nonsiblings. Our chief expectations included that competition for resources would be more intense among larger foundress groups but diminished by both larger host size and closer foundress relatedness, affecting both foundress mortality and reproductive output. From classical LMC theory, we expected that offspring group sex ratios would be less female‐biased when there were more foundresses, and from extended LMC theory, we expected that sex ratios would be more female‐biased when foundresses were close kin. We found that confinement led to the death of some females (11% overall) but only when host resources were most limiting. Mortality of foundresses was less common when foundresses were siblings. Developmental mortality among offspring was considerably higher in multi‐foundress clutches but was unaffected by foundress relatedness. Groups of sibling foundresses collectively produced similar numbers of offspring to nonsibling groups. There was little advantage for individual females to reproduce in multi‐foundress groups: single foundresses suppressed even the largest hosts presented and had the highest per capita production of adult offspring. Despite single foundress reproduction being the norm, G. nephantidis females in multi‐foundress groups appear to attune sex allocation according to both foundress number and foundress relatedness: broods produced by sibling foundresses had sex ratios similar to broods produced by single foundresses (ca. 11% males), whereas the sex ratios of broods produced by nonsibling females were approximately 20% higher and broadly increased with foundress number. We conclude that relatedness and host size may combine to reduce selection against communal reproduction on hosts and that, unlike other studied parasitoids, G. nephantidis sex ratios conform to predictions of both classical and extended LMC theories. [ABSTRACT FROM AUTHOR]

The coconut spike moth / bunch moth of oil palm, Tirathaba rufivena (Pyralidae, Lepidoptera) is reported as a pest causing varying losses in coconut and oil palm. In recent years regular and increasing incidence of this lepidopteron pest is being recorded in young and dwarf coconut palms in East Godavari District, Andhra Pradesh. A high per cent infestation was recorded in the dwarf cultivar, Ganga Bondam (12.5%) and in various cross combinations the infestation of coconut spike moth ranged from 3.5 per cent to 9.4 per cent The laboratory observations on identification of promising parasitoid for this pest revealed that gregarious ectoparasitoid i.e., Goniozus nephantidis is an effective parasitoid on T. rufivena As G. nephantidis can be successfully multiplied on large scale in laboratory therefore, the field efficacy of G. nephantidis can be explored against T. rufivena in coconut and oil palm plantations. [ABSTRACT FROM AUTHOR]

Parasitoids have the potential to suppress populations of their hosts and thus may play an important role in influencing the temporal and spatial dynamics of pest arthropods. Behavioural interactions between foraging females, collectively constituting 'mutual interference', can reduce host suppression. We use laboratory microcosms to assess the prevalence and consequences of mutual interference behaviour in a bethylid wasp, Goniozus nephantidis (Muesebeck) (Hymenoptera: Bethylidae), which is known to brood guard and to engage in agonistic contests for individual hosts and which is also an agent of biological pest control. We hold host and parasitoid numbers constant and vary the degree of female-female contact that can occur. Mutual interference is manifest in a considerable reduction in the number of offspring produced when females are not fully isolated from each other, due to effects operating at the early stages of offspring production. This mutual interference may contribute towards the limited degree of host population suppression achieved when some species of bethylids are deployed as agents of biological pest control and also has clear potential to influence the efficiency of mass rearing of parasitoids prior to field release. [ABSTRACT FROM AUTHOR]

Black-headed caterpillar, Opisina arenosella Walker (Lepidoptera: Crytophasidae) is an endemic, frequently outbreaking pest of coconut in India and Sri Lanka. It also occurs in Bangladesh and Myanmar. Two larval parasitoid wasps Goniozus nephantidis (Muesebeck) (Bethylidae) and Bracon brevicornis Wesmael (Braconidae), are widely employed, either singly or in combination, for the biological control of O. arenosella in India. The co-occurrence of G. nephantidis and B. brevicornis in the field indicates the potential for competitive interactions which may interfere with pest suppression. In order to study the outcome of competitive interactions between these parasitoids, host larvae were exposed to the parasitoid species either alone or in combination. Females of G. nephantidis and B. brevicornis did not discriminate between unparasitised hosts and hosts parasitised by the other species. Survival of G. nephantidis and B. brevicornis from eggs to adult eclosion was 89.6 and 81.8%, respectively, when larvae of O. arenosella were exposed to these parasitoids individually. When both species were released simultaneously, the survival of G. nephantidis was 86.8% and females of that species chased B. brevicornis females, attempting to bite and sting them. The mean percentage of progeny obtained was significantly higher for G. nephantidis than for B. brevicornis. G. nephantidis dominated due to its parental care behaviour producing 87.0% of progeny and a sex ratio (proportion of females) of 0.79, whereas B. brevicornis produced 84.0% progeny and a sex ratio of 0.36. Although parental care by G. nephantidis females serves to protect the progeny from intruders, it may be disadvantageous from the standpoint of pest suppression under field conditions especially, when the pest population density is high. [ABSTRACT FROM AUTHOR]

Parent investment theory predicts that parents should adjust their investment in offspring defence according to offspring value. For instance, parents should protect older, more valuable, offspring more intensively than younger offspring against a given risk of mortality. The benefits of protection may, however, vary with offspring age and parents should thus behave according to the harm that offspring would suffer in the absence of parental defence. Prior studies on this topic have focused mainly on birds and mammals with data on other taxa largely lacking. We used the parasitoid wasp Goniozus nephantidis to investigate the effect of offspring developmental stage on maternal defence against infanticidal conspecific females. On finding a host caterpillar, a G. nephantidis female paralyses it and lays eggs onto it approximately 1 day later, then remains with the offspring during development until the offspring pupate. If the host is encountered by a second female, classic owner–intruder contests ensue, with the loser being aggressively excluded from the vicinity of the host. We tested the effect of brood developmental stage on contest outcomes and also assessed the consequences of offspring age for their survival in the event that an intruder female wins the contest. We found that females defend younger offspring more than older offspring. Explanations for this behaviour are discussed in terms of owner–intruder asymmetries in resource value and the ‘harm to offspring hypothesis’. [Copyright &y& Elsevier]

Females of the parasitoid wasp Goniozus nephantidis paralyse host caterpillars and lay a clutch of up to 18 eggs onto the host integument. The known biology of G. nephantidis suggests that matings occur exclusively between siblings from the same brood. This leads to the prediction that brood sex ratios should be highly female-biased and have low variance. Sex ratios are indeed female-biased, with the mean proportion of males equal to 0.093. However, while sex ratio variance is significantly less than binomial, many broods contain no males at emergence. During development 28% of G. nephantidis offspring die. Male mortality offers a potential explanation for all-female (= virgin) broods. For the clutch sizes and mortality observed, theory predicts that <10% of females will emerge from all-female broods but the empirical value is much higher. The prediction that the prevalence of virginity decreases with increasing clutch size is, however, supported. We consider alternative explanations for the observed proportion of all-female broods, but this appears to be neither an artefact of the laboratory environment nor due to incorrect assumptions about G. nephantidis life history. Although its reproductive biology has been much investigated and its sex ratio matches some theoretical predictions, we conclude that a fuller understanding of G. nephantidis sex ratio requires a deeper knowledge of its field biology. [ABSTRACT FROM AUTHOR]