Light pollution is a driver of insect declines

The night‐time environment is increasingly being lit, often by broad‐spectrum lighting, and there is growing evidence that artificial light at night (ALAN) has consequences for ecosystems, potentially contributing to declines in insect populations. Moths are species‐rich, sensitive to ALAN, and have undergone declines in Europe, making them the ideal group for investigating the impacts of light pollution on nocturnal insects more broadly. Here, we take a life cycle approach to review the impacts of ALAN on moths, drawing on a range of disciplines including ecology, physiology, and applied entomology. We find evidence of diverse impacts across most life stages and key behaviours. Many studies have examined flight‐to‐light behaviour in adults and our meta‐analysis found that mercury vapour, metal halide, and compact fluorescent bulbs induce this more than LED and sodium lamps. However, we found that ALAN can also disrupt reproduction, larval development, and pupal diapause, with likely negative impacts on individual fitness, and that moths can be indirectly affected via hostplants and predators. These findings indicate that ALAN could also affect day‐flying insects through impacts on earlier life stages. Overall, we found strong evidence for effects of artificial light on moth behaviour and physiology, but little rigorous, direct evidence that this scales up to impacts on populations. Crucially, there is a need to determine the potential contribution of ALAN to insect declines, relative to other drivers of change. In the meantime, we recommend precautionary strategies to mitigate possible negative effects of ALAN on insect populations.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/icad.12447

Is light pollution driving moth population declines? A review of causal mechanisms across the life cycle

CHAPTER 4: Sexual Selection and the Evolution of Butterfly Mating Systems

Background Grapholita molesta (Busck) is a fruit pest worldwide. While sex pheromones-based technology for male attraction has made great progress in the monitoring or mass trapping of G. molesta, the attraction of males alone is not an effective reproductive control strategy. The integration of sex pheromones with female attractants, which have been reported to attract adult females and males, is therefore necessary. To determine a suitable dual-sex attractant for trapping G. molesta, combinations of four attractants [sex pheromones (ph), host-plant volatiles (pp), sugar-acetic acid-ethanol-water solutions (ss), and food lures (fl)] were screened using electroantennograms, wind tunnel experiments, and field trial tests. Various mediums and antioxidants were then added to the selected attractants combination (AC) and examined in the field. Results The responses of G. molesta to attractants differed significantly between the sexes. Increases in male activation behavior and trapping were motivated by ph, while pp and particularly ss increased adult antennae perception. In response to fl alone or together with ph, more male or female individuals were trapped. This indicates that ph, as a sex lure, and fl, as a host lure, may complete male and female attraction. Consequently, this combination is suggested. In the field trials, the additions of 10 μL of honey and 35% (184.3 μg) of 2,6-di-tert-butyl-4-methylphenol [BTH] (preservatives) to the AC (ph + fl) resulted in moth captures equal to that of a commercial sex pheromones lure. Conclusion A dual-sex attractant composed of ph, fl, honey, and BTH is recommended for trapping G. molesta in the field. © 2020 Society of Chemical Industry.

Behavioral effects of different attractants on adult male and female oriental fruit moths, Grapholita molesta.

For oligophagous insects, larval performance is very important to evaluate host suitability in host use. However, key indices among all performance traits including survival, development, and fecundity of the adult insect to predict host suitability are not clear. To investigate the key performance indices, we observed the performance of an oligophagous moth Grapholita molesta (Busck) (Lepidoptera: Tortricidae), a pest mainly damaging rosaceous plants, on three apple varieties, three peach varieties, and three pear varieties in the laboratory by placing its eggs on fruits. The moth's fitness was evaluated by the intrinsic rate of increase at fruit variety- and species-level variability. Our results showed that the preovipositional period of female moths and longevity of male moths were the indices primarily predicting intrinsic rates of increase for fruit variety and for fruit species. However, the preovipositional period of female moths was different at species-level variability but not at variety-level variability, whereas the longevity of male moths was not different at variety- or species-level variability. These results revealed that preovipositional period of female moths was a key predictor for host suitability in G. molesta. This study highlighted that gravid females may be a principal indicator in host resource optimization for oligophagous insects.

Importance of Preovipositional Period of an Oligophagous Moth in Predicting Host Suitability.

Host plants will affect the performance and population dynamics of the polyphagous insect pest Grapholitha molesta (Busck) (Lepidoptera: Tortricidae). Cultivar‐level variability needs to be considered in assessing the performance of G. molesta. We evaluated the fitness of G. molesta on five apple varieties in the laboratory by placing eggs on apples and observing their performance including survival, development, and fecundity of the adult insect. Our results demonstrated differences between indices such as larval duration, pupal weight, egg production, length of tunnel, and exiting rate of larvae, which gave similar host rankings. Variety Danxia was less suitable than Jinqing and Shuohong, and more suitable than Empire and Jinxing. However, other indices such as pupal duration, total pre‐oviposition time, and the estimated population parameters resulted in a different host ranking. We calculated weighted fitness scores to overcome the problem of inconsistent rankings. Empire changed from being the second highest ranking variety based on all population parameters to the second lowest using weighted fitness scores. The difference in ranking observed between apple varieties demonstrates the care needed in predicting population performance in the field using single traits.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/eea.12655

Methods to measure performance of Grapholitha molesta on apples of five varieties

The Oriental fruit moth, Cydia molesta (Busck, 1916) (Lepidoptera: Tortricidae), is a key pest of fruit and is widely distributed around the world. There are important connections between its behav...

Emergence and mating behavior of the oriental fruit moth Cydia molesta (Lepidoptera: Tortricidae) and its potential for reproduction

Oriental fruit moth, Grapholita molesta (Busck), is a worldwide pest and is the dominant pest of rosaceous plants in northern China. Little is known, however, about the influence of abiotic factors on the daily life history events of this economically important pest, so here we evaluated the effect of different photoperiods (L:D) (0:24; 2:22; 4:20; 6:18; 8:16; 10:14; 12:12; 14:10; 15:9 [control]; 16:8; 18:6; 20:4; 22:2; and 24:0 h) and light intensities (50, 100, 200, 300, 400, and 500 lux) on the mating behavior and reproduction of oriental fruit moth. We found that oriental fruit moth adults with an 8, 9, or 10 h scotophase showed considerably more courtship behavior than those in other photoperiod treatments. Meanwhile, male fanning and male ‘crawling in a circle’ behaviors significantly decreased with increasing light intensity. Neither female or male oriental fruit moth longevity nor the egg hatch rate were influenced by photoperiod (P = 0.146; 0.271; 0.107) or light intensity (P = 0.268; 0.08; 0.123). In both photoperiod and light intensity treatments (P < 0.05), the number of eggs laid daily by females was significantly influenced by female age, decreasing with greater age. Female oriental fruit moth lifetime fecundity was influenced by photoperiod, with the 9, 10, 16, 18, and 22 h scotophase periods having higher fecundity than other treatments. Meanwhile, fecundity decreased with increasing light intensity.

Yi Wang

Papers

Behavioral effects of different attractants on adult male and female oriental fruit moths, Grapholita molesta.

Methods to measure performance of Grapholitha molesta on apples of five varieties

Importance of Preovipositional Period of an Oligophagous Moth in Predicting Host Suitability.

Emergence and mating behavior of the oriental fruit moth Cydia molesta (Lepidoptera: Tortricidae) and its potential for reproduction

The Effect of Photoperiods and Light Intensity on Mating Behavior and Reproduction of Grapholita molesta (Lepidoptera: Tortricidae)