Insect quantity is an important index for determining the degree of damage to plants.  The brown planthopper (BPH), Nilaparvata lugens (Stål), is one of the most important rice pests in Asia.  Here, we used two genotypes of BPH, a high-fecundity genotype (HFG) and a low-fecundity genotype (LFG), to measure their ecological fitness and to explore possible causes for genotype differentiation by transcriptome sequencing.  Our results showed that there were significant differences in body weight, egg hatching rate and honeydew secretion between the HFG and LFG, particularly, the number of eggs laid per female was more significant.  Transcriptional analysis showed that a total of 1 966 differentially expressed genes (DEGs) were mainly involved in energy metabolism, carbohydrate and lipid synthesis, insect hormone synthesis and fecundity-related pathways.  Moreover, we found that the phosphorylation levels of AMPK, AKT and FoxO and the synthesis of ecdysone were different between the two genotypes of BPH.  These findings may partially explain the difference in the ecological fitness between HFG and LFG.  This study is the first to compare the differences between two genotypes of BPH and to provide transcriptomic evidence to further understand the fecundity of BPH.

 

Ophraella communa (Coleoptera: Chrysomelidae), the ragweed leaf beetle, is a biological control agent of the invasive common ragweed, Ambrosia artemisiifolia (Asterales: Asteraceae).  Adults can survive cold conditions that occur during winter.  The adults mate before entering overwintering.  Understanding the connection between copulation and overwintering will be useful for determining O. communa seasonality.  Determining the relationship between overwintering and copulation required comparison of mated and unmated beetles at mean lethal temperature (LTemp₅₀) exposures for 2 h.  Cold-related physiological indices, including the water ratio, super cooling point (SCP), cryoprotectant levels, and energy reserve levels, were also measured.  Mating treatment decreased the LTemp50 of both sexes by reducing their mean SCP and water ratios.  Although the changes of cryoprotectant levels in mated adults were not precisely consistent in between the genders, they increased greatly in both males and females.  Body sugar may play a role in copulation and may also elevate cold hardiness in O. communa.