No abstract

Supplemental nutrients of adult moths maximize moth fitness and contribute to the pollination of many plants. Previous reports have revealed that sugar feeding promotes to sex pheromone biosynthesis by increasing the haemolymph trehalose concentration in mating moths. Here, Mythimna separata adults were employed as a model to investigate the effect of sugar feeding on sex pheromone biosynthesis. Results showed that in virgin females, sugar feeding markedly increased the concentrations of trehalose, pyruvic acid, and acyl-CoA in pheromone glands (PGs), which in turn led to an increase in sex pheromone titer, female ability to attract males and successfully mating frequency in sugar-fed females. Consistently, sugar-fed females laid more eggs than water-fed females. Furthermore, the refeeding of starved females also caused significantly increase in the concentrations of trehalose, pyruvic acid, and acyl-CoA in PGs, thus facilitating a significant increase in sex pheromone production. Most importantly, RNAi-mediated knockdown of trehalase (leading to PG starvation) resulted in an increase in trehalose content, and decrease in the concentrations of pyruvic acid, and acyl-CoA in PGs, which in turn led to a decrease of sex pheromone titer, female ability to attract males and successful mating efficacy. Altogether, results revealed a mechanism by which sugar feeding contributed to trehalose utilization in PGs, promoted to significantly increased sex pheromone precursor by increasing the concentrations of pyruvic acid and acyl-CoA, and facilitated to sex pheromone biosynthesis and successful mating.

The presence of adequate nectar sources along the migratory pathway is a prerequisite for moths of oriental armyworm, Mythimna separata, to reach target habitats and lay eggs. Identification of plant species and assessment of their suitability as wild nectar sources along the summer migration pathway of adult M. separata are critical steps in making effective forecasts of second-and third-generation armyworm outbreaks in North China. We explored five aspects of moth-nectar source relationships: (1) Field investigations in 2014 and 2015 showed that the florescence of chaste tree, Vitex negundo var. heterophylla, a primary nectar plant in apiculture, coincided with the summer migration of oriental armyworm moths. The flowers of chaste tree opened day and night and M. separata moths were found actively flying around and resting on tree. (2) Identification of moth-borne pollen by scanning electronic microscopy (SEM) micrographs in 2015 and 2016 revealed that 15.4% of 369 moths trapped by blacklight traps, 17.1% of 557 moths captured by vertical-pointing searchlight traps and 24.4% of 311 moths caught by pheromone traps were found with pollen attached to their proboscis. A total of 228 pollen-carrying individuals out of 1 237 armyworm moths were captured by the three types of traps. The three highest percentages of pollen-bearing armyworm moths were carrying pollen of Toona sp. (59.65%), Ligustrum sp. (27.19%) and Syringa sp. (4.39%). In total, 14 types of pollen were detected where three were identified to species, 10 to genus and one as an unknown species. (3) Analysis of geographical distribution, flowering periods and relative abundances of candidate nectar plants suggested that Chinese toon, Toona sinensis, and Privet, Ligustrum lucidum, were two important nectar plant species. (4) Analysis on relationship between pollen and ovarian development showed that 14, 15 and 10 females carrying pollen of T. sinensis had ovaries at developmental stages I, II and III, respectively. Many T. sinensis pollen grains were present on the proboscises of female moths. (5) Comparison of trap effectiveness between blacklight and vertical-pointing searchlight traps indicated blacklight traps caught the highest proportion (35.2%) of female in ovarian stage V, whereas vertical-pointing searchlight traps caught the highest proportion (43.5%) of female in ovarian stage I with additional proportions of decreasing percentages for stages II, III and IV. Integrated analysis on these five aspects suggests that T. sinensis is an important, suitable summer nectar source that potentially influences migration and reproduction of M. separata moths and

Holotrichia parallela damages seriously on peanut (Arachis hypogaea) pods. Elucidation of its flight and walking performance in the presence of different plants may provide an insight in its host selection process and an explanation to its strong olfactory preference to an attractive nonhost, castor bean (Ricinus communis). We determined the relationships among flight performance, mate choice, and body weight of H. parallela beetles, and then investigated their flight and walking patterns in the presence of known hosts and attractive nonhost plants using a flight mill and a locomotion compensator, respectively. Body weights were not related to mating success, regardless of sex. The flight proportion of selected females drastically decreased compared with nonselected females, nonselected males, and selected males. Within mated males, heavier individuals exhibited poorer flight performance than lighter ones. In flight bioassay, peanut showed an arrestment effect on virgin females. For walking activity factors (distance, time, and speed), the host plants velvetleaf (Abutilon theophrasti) and Siberian elm (Ulmus pumila) elicited the strongest responses in females and males, respectively. Interestingly, the most preferred adult host, Siberian elm, and the nonhost, castor bean, elicited the highest values of two orientation factors (orientation and upwind length) in females. The chemical similarity hypothesis, which states that feeding or oviposition of insects mistakenly on nonhost can be traced to their chemical similarity to actual hosts, could explain the attraction of H. parallela to castor bean.

Experience is well known to affect sensory-guided behaviors in many herbivorous insects. Here, we investigated the effects of natural feeding experiences of Helicoverpa armigera larvae on subsequent preferences of larval approaching and feeding, as well as the effect of host-contacting experiences of mated females on subsequent ovipositional preference. The results show that the extent of experience-induced preference, expressed by statistical analysis, depended on the plant species paired with the experienced host plant. Larval feeding preference was much easier to be induced by natural feeding experience than larval approaching preference. Naïve larvae, reared on artificial diet, exhibited clear host-ranking order as follows: tobacco ≥ cotton > tomato > hot pepper. Feeding experiences on hot pepper and tobacco could always induce positive feeding preference, while those on cotton often induced negative effect, suggesting that the direction of host plant experience-induced preference is not related to innate feeding preference. Inexperienced female adults ranked tobacco as the most preferred ovipositional host plant, and this innate preference could be masked or weakened but could not be reversed by host-contacting experience after emergence.

No abstract

No abstract

No abstract