No abstract

Heat shock proteins (Hsps) have been linked to stresses and winter diapause in insects, but whether they are components of summer diapause is still unknown. In this study, complementary DNAs of Hsp90 from Pieris melete, Pieris rapae and Pieris canidia named PmHsp90, PrHsp90 and PcHsp90, respectively, were cloned and sequenced. The deduced amino acid sequence consisted of 718 amino acid residues with a putative molecular mass of 82.6, 82.6 and 82.7 kDa, respectively. The amino acid sequences contained all of the five conserved signature motifs in the Hsp90 family and a bHLH protein folding activity region. The differential expression pattern of PmHsp90 in response to summer diapause and winter diapause, which are related to heat/cold stress, was investigated. Cold stress induced Hsp90 up-regulation in summer and winter diapause pupae, but not in non-diapause individuals. Heat shock up-regulated PmHsp90 gradually with an increase in temperature in summer diapause, and PmHsp90 was rapidly up-regulated in winter diapause. After 30 min heat shock at 39°C, substantial up-regulation of PmHsp90 transcript levels were observed both in summer and winter diapause. However, in non-diapause a relatively stable expression was found under different durations of 39°C heat shock. Compared to the optimal treatment of 18°C for diapause development, a high temperature acclimation of 31°C induced PmHsp90 up-regulation in summer diapause, whereas a low temperature acclimation of 4°C induced up-regulation in winter diapause. The current results indicate that Hsp90 may play an important role in response to heat/cold stress both in summer and winter diapause.

Sampling flower-visiting insects in agricultural fields at large spatial and temporal scales is significant for understanding local insect pollinator communities. The most commonly used method, pan trap, has been criticized due to its attractant bias. A window trap (also referred to as the flight-intercept trap) is a non-attractant sampling method, which has been applied in forests and grasslands, but rarely in agricultural fields. We aim to test whether we can replace pan traps with window traps in agricultural fields by comparing species richness and species composition between the two methods, and to show whether flower-visiting insects collected in both traps can reflect flower-visiting activity recorded by camera observation. We conducted a 2-year study to compare the performance of these sampling methods in an oilseed rape field. Results showed that the relative abundance of dominant flower-visiting species was highly correlated between the window trap and the pan trap samples, while window traps caught more individuals and higher (rarefied) species richness than pan traps. The species composition of window traps was more similar to each other than that of pan traps. The proportion of honey bees (Apis spp.) collected in both traps underestimated their flower-visiting activity recorded by camera observations, while sweat bees (Halictidae) and butterflies (Lepidoptera) were overestimated. Our study suggests that the window trap has the potential to serve as an alternative sampling method of flower-visiting insects to the pan trap. However, we need to be cautious when using specimens caught in both traps as a proxy of their flower-visiting activity.

The brown plant hopper, Nilaparvata lugens Stål, is a major rice pest in SouthEast Asia. While brown plant hopper (BPH) populations can be regulated by natural enemies, there is limited quantitative information available about the contribution of different predator species to BPH mortality. Our study has three aims: (i) assess the relative contribution of different predator species to BPH mortality in rice fields, (ii) assess diurnal patterns in BPH predation, and (iii) assess the seasonal variation in BPH predation. We quantified predation of live mobile BPH in three rice fields using video recording and assessed densities frogs, a major predator group, by direct counts. In 864 hours of video recording, 102 mortality events were observed. Frogs (Ranidae), wolf spiders (Lycosidae) and jumping spiders (Salticidae) were the main predators, accounting for 76%, 13% and 9% of the BPH predation events, respectively. There were large differences in frog density across fields, and there was more predation during the evening (63% predation events) than during the day (37%). Survival analysis indicated that predation risk quickly decreased with time after the onset of recording sessions and that most predation happened within the first 10 minutes. The results confirm the often overlooked contribution of frogs to BPH predation, but also highlight the substantial variation in predator pressure and frog abundance across farmers' fields. While camera observations provide compelling information on the identity and relative importance of natural enemies in predation of pests, further development of methods is needed to minimize possible biases resulting from disturbance when making camera observations to quantify predation risk.