The fall armyworm (FAW), Spodoptera frugiperda, is a highly polyphagous lepidopteran pest, with its growth and adaptation affected by different host plants. However, little is known about the effects of host plants on ovarian development in this species. Thus, we evaluated the effects of feeding on corn (Zea mays L.) and goosegrass (Eleusine indica), on the ovarian development of S. frugiperda. Using various stages of S. frugiperda, we also evaluated the larval and pupal weights, number of eggs, and differentiation of ovarioles over time. Results showed that females fed on goosegrass had shorter ovarioles and laid less eggs than those fed on corn. Transcriptome analysis identified 3,213 genes involved in ovarian development in the fall armyworm. Of these, 881 genes were differentially expressed when fed on corn and goosegrass. The analysis also indicated that the hormone biosynthetic pathways may be involved in the reproductive system. In relation to the reproductive function, nine juvenile hormone (JH) biosynthetic genes, four 20-hydroxyecdysone (20E) biosynthetic genes, and four ovary-relevant functional genes were identified. The time course of the expression profiles of these hormone- and ovary development-related genes was measured by quantitative real-time PCR (qRT-PCR). In total, six of them showed a decreasing trend in the ovary of the FAW fed on goosegrass, while two genes showed an increasing trend. Our results showed that significant changes in the reproductive activity/ovary development in the FAW occurred in response to different diets. These results serve as bases for evaluating how optimal host plants and feeding preference affect ovarian development in the FAW.

Spodoptera frugiperda (J.E.Smith) (Lepidoptera: Noctuidae) is an invasive pest that ravaging crops in many provinces of China. In order to specifically control this invasive pest, understanding of the relationship between the insect and the hosts is necessary. In this study, we have compared the biological and nutritional indices of S. frugiperda by feeding it with five different host-plants (Zea mays, Triticum aestivum, Digitaria sanguinalis, Glycine max and Eleusine indica) under laboratory conditions. The biological and nutritional indices of Z. mays feeding S. frugiperda were the best. However, the pupa weight and fecundity of S. frugiperda fed with G. max and E. indica were significantly lower than those fed with other hosts, efficiency of conversion of digested food (ECD) and efficiency of conversion of ingested food (ECI) were also lower than others. The total phenol content of hosts was negatively correlated with the growth and nutrient accumulation of S. frugiperda, while the C/N content was positively correlated. When fed on different host plants, the biological and nutritional indices of S. frugiperda were different, but all of them could complete the life cycle. Therefore, S. frugiperda also has a tendency to feed on other hosts, especially plants with high C/N content, when Z. mays is insufficient.