Polyandry and trade-off between fecundity and longevity in female Dichelops furcatus (Hemiptera: Pentatomidae)

Polyandry contributes to Gonipterus platensis (Coleoptera: Curculionidae) rearing

Background

Gonipterus platensis Marelli, 1926 (Coleoptera: Curculionidae) is one of the main defoliating beetles in Eucalyptus plantations. Biological control with egg parasitoids is one of the main control strategies for this pest and a constant supply of fresh host eggs is required to rear the parasitoids. Polyandry can influence Gonipterus oviposition by increasing female fecundity and fertility; however, the high density of individuals in laboratory colonies can lead to male harassment, resulting in lower reproduction rate. The aim of this study was to measure the effects of monoandry and polyandry on the reproduction of G. platensis and the effects of male harassment on laboratory rearing conditions.

Methods

Reproductive parameters were compared between three treatments: monoandry, where the female was allowed to mate daily with the same male; no choice polyandry, where the female was allowed to mate daily with a different male; and polyandry with choice, where the female was allowed to mate daily, but with a choice between five different males. Another experiment varying the density of males was conducted to evaluate the effect of male harassment.

Results

Polyandry with choice resulted in the longest period of oviposition, highest fecundity and highest number of eggs per egg capsules when compared to monoandrous females. No negative effect related to male harassment in the laboratory, such as decreased fertility, fecundity, or number of eggs per egg capsule, was detected.

Conclusion

Polyandry contributes to mass rearing as it increases fecundity and oviposition period on females and there is no evidence of male harassment on G. platensis.

Gene Editing and Genetic Control of Hemipteran Pests: Progress, Challenges and Perspectives

The origin of the order Hemiptera can be traced to the late Permian Period more than 230 MYA, well before the origin of flowering plants 100 MY later in during the Cretaceous period. Hemipteran species consume their liquid diets using a sucking proboscis; for phytophagous hemipterans their mouthparts (stylets) are elegant structures that enable voracious feeding from plant xylem or phloem. This adaptation has resulted in some hemipteran species becoming globally significant pests of agriculture resulting in significant annual crop losses. Due to the reliance on chemical insecticides for the control of insect pests in agricultural settings, many hemipteran pests have evolved resistance to insecticides resulting in an urgent need to develop new, species-specific and environmentally friendly methods of pest control. The rapid advances in CRISPR/Cas9 technologies in model insects such as Drosophila melanogaster, Tribolium castaneum, Bombyx mori, and Aedes aegypti has spurred a new round of innovative genetic control strategies in the Diptera and Lepidoptera and an increased interest in assessing genetic control technologies for the Hemiptera. Genetic control approaches in the Hemiptera have, to date, been largely overlooked due to the problems of introducing genetic material into the germline of these insects. The high frequency of CRISPR-mediated mutagenesis in model insect species suggest that, if the delivery problem for Hemiptera could be solved, then gene editing in the Hemiptera might be quickly achieved. Significant advances in CRISPR/Cas9 editing have been realized in nine species of Hemiptera over the past 4 years. Here we review progress in the Hemiptera and discuss the challenges and opportunities for extending contemporary genetic control strategies into species in this agriculturally important insect orderr.

Effects of Different Temperatures on the Development and Reproduction of Sitobion miscanthi From Six Different Regions in China

The increase in temperature caused by global warming has greatly impacted plant growth and pest population dynamics worldwide, especially for wheat aphids. In this study, Sitobion miscanthi individuals from six geographic populations located in different wheat-producing areas in China were compared with regard to their growth, development, survival, and reproductive under different temperature conditions (17, 22 and 27°C). A population life-table analysis and a correlation analysis between geographic factors and S. miscanthi longevity or fecundity were also performed. Temperature significantly affected the nymphal development duration (NDD), the adult longevity (ALY) and the fecundity (AFY) of the aphids, however, latitude can only affect the NDD and ALY. There is an obvious interaction between temperature and latitude on the NDD, ALY, and AFY. The NDD in the three northern populations was significantly shorter than that in the southern populations. The ALY in northern populations was significantly longer than that in southern populations at different temperatures. Except for Yinchuan population was no significantly different under different degrees, the ALY of other populations was significantly shortened at 27°C. The AFY of northern populations was significantly lower than that of southern populations at 22°C, while significantly higher at 27°C. With the increase of temperature, the fecundity of northern population gradually decreased from 17 to 22°C, while the southern population suddenly decreased at 27°C. The curves of survival rate (sxj) in southern populations were significantly shorter than that of northern population. Especially the populations in Suzhou and Wuhan, in which the survival rate decreased rapidly at 27°C. Age-specific survival rate (lx) of southern populations began to decline rapidly on 15 days of age at 27°C, while those of northern populations were not significantly affected until on 20 days of age. The highest peaks of age-stage fecundity (fxj), age-specific fecundity (mx), and age-specific net maternity (lxmx) were occurred in northern populations. In addition, there was a positive correlation between latitude and longevity under the three degrees, however, only at 27°C, there was a positive correlation between latitude and fecundity. Our result proved that the higher reproductive rate of southern population requires aphids to live at the suitable ambient temperature, and aphid populations in the north have a wider ecological amplitude. The results will be helpful for predicting the potential aphid outbreaks in China’s main wheat areas under suitable conditions.

Wide Diurnal Temperature Amplitude and High Population Density Can Positively Affect the Life History of Sitobion avenae (Hemiptera: Aphididae)

Diurnal temperature amplitude is known to have a large influence on insect life history. Population density affects intraspecific competition and many other aspects of insect life history. However, there is limited information on the interactive effects of these factors on insects. Here, we tested the interactive effects of three diurnal temperature amplitudes (22 ± 0°C, 22 ± 6°C, and 22 ± 12°C) and three population densities on the development, survival, longevity, and fecundity of the English grain aphid Sitobion avenae (Fabricius) (Homoptera: Aphididae). At a constant temperature, increasing population density reduced the growth and survival of early-instar nymphs, increased longevity, and reduced fecundity. At a low population density, increasing temperature amplitude inhibited nymph development. However, even at a high temperature amplitude, nymph survival rate was higher than expected, and reproduction was possible because the recovery of the lower night-temperatures eliminated thermal stress. Increasing the population density reduced, and even reversed, the negative effects of the wide temperature amplitude. This may reflect synergistic interactions between population density and wide temperature amplitude as these stressors each incur energetic costs. These findings emphasize the importance of temperature amplitude and population density for improving prediction accuracy and damage assessment during pest control modeling.