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Voltinism and life‐history traits of the invasive fall armyworm (FAW) Spodoptera frugiperda were investigated under semi‐natural conditions for a period of 2 years. The FAW invaded the corn field in the suburbs of Nanchang (28°46′ N, 115°50′ E) in early summer and produced six complete generations. FAW had the characteristics of short developmental time, high survival rates and strong fecundity. The development time of female pupae was significantly faster than that of male pupae, resulting in the emergence of female pupae earlier than male pupae. Except for the sixth generation in 2021, there was no significant difference between female and male sex ratio, which was close to 1:1. FAW showed male‐bias sexual size dimorphism with male pupae being significantly larger than female pupae. Unlike pupal weight, in most generations, male adult weighed significantly less than females, because the weight loss of male pupae during metamorphosis was significantly greater than that of female pupae. The temporal variation of pupal weight did not conform to the temperature–size rule. Compared with 22.8°C, the 29.2°C high temperature not only significantly reduced the development time of larvae but also significantly increased pupal weight. The adult fecundity feeding on fresh corn leaves was higher than that feeding on live corn plants in most generations. In most generations, pupal weight was positively correlated with larval development time and adult weight was positively correlated with fecundity. In conclusion, climate differences between generations and years have significant effects on developmental time, body weight, sexual size dimorphism and fecundity of the FAW. These results add to the understanding of the evolution of life‐history traits in the FAW and may have important implications for predicting population dynamics of the FAW and optimising control strategies. [ABSTRACT FROM AUTHOR]

The fall armyworm (FAW) Spodoptera frugiperda (J. E. Smith; Lepidoptera; Noctuidae) has invaded Jiangxi Province, Southeast China for the past 3 years. Although the FAW displays a wide host range, its main host plants in Jiangxi Province are field corn. Understanding the population dynamics of the FAW on different host plants is critical for developing an appropriate control strategy. This study investigated the effects of food plants (corn, peanut, soybean and sugarcane) on life‐history traits of FAW and tested the leaf contents of the total flavonoids, reducing sugars, sucrose and C/N ratio of these host plants. We found that the FAW fed on corn leaves exhibited significantly shorter larval and pupal development times, larger body weight, higher growth rate, lower weight loss, smaller sexual size dimorphism, shorter preoviposition period and higher fecundity than those fed on peanut, soybean and sugarcane leaves. The FAW showed a protogyny phenomenon because the pupal development stage was significantly longer in males than females. Food plants changed the relationships between larval development time and pupal weight and between fecundity and longevity. The corn leaves showed significantly higher contents of reducing sugars and sucrose, lower content of the total flavonoids and a moderate C/N ratio compared with the other leaves, suggesting that the corn leaf tissues are more nutritious. Our results provide the most comprehensive information about the life‐history traits of this newly invasive pest. These findings may help us understand why the FAW mainly infests corn plants and may be critical for the development of strategies to predict infestation levels. [ABSTRACT FROM AUTHOR]

A southern population (S) from Xiushui County (29°1′N, 114°4′E) and a northern population (N) from Shenyang city (41°48′N, 123°23′E) of the cabbage beetle, Colaphellus bowringi vary greatly in their life-history traits, and may serve as an excellent model with which to study the inheritance of life-history traits. In the present study, we performed intraspecific hybridization using the two populations, comparing the key life-history traits (fecundity, development time, body weight, growth rate, and sexual size dimorphism (SDD)) between the two populations (S♀ × S♂ and N♀ × N♂) and their two hybrid populations (S♀ × N♂ and N♀ × S♂ populations) at 19, 22, 25, and 28°C. Our results showed that there were significant differences in life-history traits between the two parental populations, with the S population having a significantly higher fecundity, shorter larval development time, larger body weight, higher growth rate, and greater weight loss during metamorphosis than the N population at almost all temperatures. However, these life-history traits in the two hybrid populations were intermediate between those of their parents. The life-history traits in the S × N and N × S populations more closely resembled those of the maternal S population and N population, respectively, showing maternal effects. Weight loss for both sexes was highest in the S population, followed by the S × N, N × S, and N populations at all temperatures, suggesting that larger pupae lost more weight during metamorphosis. The changes in SSD with temperature were similar between the S and the S × N populations and between the N and the N × S populations, also suggesting a maternal effect. Overall, our results showed no drastic effect of hybridization on C. bowringi, being neither negative (hybrid inferiority) nor positive (heterosis). Rather, the phenotypes of hybrids were intermediate between the phenotypes of their parents. [ABSTRACT FROM AUTHOR]

In mid‐May, 2019, the fall armyworm (FAW) Spodoptera frugiperda invaded Jiangxi Province, China, and caused extensive damage to corn crops. However, little attention has been given to the life‐history traits of the FAW. In the present study, we systematically investigated the life‐history traits of the newly invasive FAW on corn leaves at 19, 22, 25, 28, and 31°C under a photoperiod of LD 15:9 hr. The FAW thrived on the corn leaves with short developmental periods, high survival rates of larvae and pupae, very high mating success rates, and high fecundity. The pupal developmental stage was significantly longer in males than females at all temperatures, thus resulting in a protogyny phenomenon. The pupal weight was heaviest after a relatively shorter larval development stage at a higher temperature (25°C); thus, the FAW did not follow the temperature–size rule. Females were smaller than males, indicating sexual size dimorphism. A small proportion of females delayed their pre‐oviposition period and began to lay eggs on the 7th to 9th day after adult emergence. There were positive relationships between pupal weight and larval developmental time and between adult weight and fecundity. There was a negative relationship between fecundity and longevity. These findings can help us to predict the population dynamics of the FAW on corn and to develop a suitable and practical management strategy. [ABSTRACT FROM AUTHOR]

It is generally thought that females preferentially mate with novel males rather than with males with which they have recently mated and polyandry can lead to greater reproductive success. We first examined female mate preference and then compared mating duration and female fitness between monogamy and polyandry in the cabbage beetle, Colaphellus bowringi Baly. In a simultaneous choice test, the majority of females remated with familiar males rather than novel males. Mating also lasted longer with familiar males. In a second experiment, monogamous females lived longer than polyandrous females. Although there was no significant difference in egg production between monogamous and polyandrous females, the former produced more viable eggs, with a higher hatching rate. These results suggest that monogamy is more advantageous for female fitness than polyandry in C. bowringi. [Copyright &y& Elsevier]

Circadian mating rhythms, mating frequency, mating duration, and the effect of mating duration on fecundity and fertility in the cabbage beetle, Colaphellus bowringi were investigated in the laboratory. Mating occurred throughout the 24-h cycle but the majority of copulations occurred in the photophase with two apparent peaks, one at 8:00 and another at 16:00. Mating frequency observations for 10 consecutive days indicated that pre-mating period of C. bowringi was about 4 days, and pairs mated an average of 5 times per day and an average of 40 times during the first 10 days. There was a negative correlation between mating frequency and mating duration during the consecutive mating. The mean duration of the first copulation (136.24 ± 4.62 min) was significantly longer than those of the second (57.87 ± 2.03 min), third (53.05 ± 2.05 min) and fourth copulation (30.86 ± 2.98 min). Fecundity showed a slight increase with increasing mating duration but no significant difference among treatments. However, fertility was significantly influenced by the mating duration in this species. Mating of 20-min duration did not produce viable eggs. The mean percentage of fertile eggs with completed mating duration (204.43 ± 18.96 min, 56.75% fertile eggs) was significantly higher than those with 60 min (39.55%) and 30 min (17.91%) mating duration, suggesting that the longer mating duration might be associated with transfer of more sperm that are used to increase the fertility of eggs. [ABSTRACT FROM AUTHOR]