Comparing the Performance of Hyphantria cunea (Lepidoptera: Arctiidae) on Artificial and Natural Diets: Feasibility of Mass-Rearing on Artificial Diets

The combined multilayer perceptron and logistic regression (MLP-LR) method better predicted the spread of Hyphantria cunea (Lepidoptera: Erebidae)

Hyphantria cunea (Lepidoptera: Erebidae) is one of the pests that pose a serious threat to forest and agronomic crops in China. Its spread is influenced by various factors, including environmental factors and anthropogenic factors, and the available data on pest spread and the influencing factor has nonlinear relationship. Additionally, the collection of pest data is often constrained, resulting in small datasets, a lack of long-term time series data, and issues such as missing data and anomalies. Traditional model-driven approaches have limitations in handling nonlinear relationships and high-dimensional data, while data-driven methods often lack interpretability and are prone to overfitting, ultimately leading to insufficient prediction accuracy. Therefore, this paper proposes the MLP-LR method, which combines logistic regression (LR) with a multilayer perceptron (MLP) to overcome these limitations. The model also used the Bayesian adaptive lasso method to select important influencing factors, that further improved the prediction accuracy. Based on H. cunea occurrence data in China, the current study demonstrated the stability and accuracy of the MLP-LR model on small datasets. The results showed that compared to traditional LR models and MLP independently, MLP-LR performs better in predicting the spread of H. cunea, effectively addressing the shortcomings of traditional methods. This study provides a new tool and perspective for forecasting and early warning of H. cunea outbreaks, offering important references for future research and its applications in the field.

Suitability of Artificial Diets Containing Various Types of Pollen Grains to Helicoverpa armigera (Hübner, 1808): Nutritional Performance and Digestive Enzyme Response

The development of an effective artificial diet is essential for the mass rearing of insects used in pest management programs, including augmentative biological control, insecticide resistance monitoring, and sterile insect release. This study evaluated the consumption, utilization, and enzymatic responses of the polyphagous pest Helicoverpa armigera (Hübner, 1808) (Lepidoptera: Noctuidae) when reared on meridic diets supplemented with different pollen grains. The control diet followed a well-established meridic formulation, while the eight experimental diets incorporated pollen from the honey bee, rapeseed, maize, sunflower, hollyhock, glossy shower, saffron, and date palm. The findings indicate that pollen supplementation enhances the quality of artificial diets for H. armigera. Larvae fed on the date palm pollen-supplemented diet exhibited significantly higher weight gain, efficiency of conversion of ingested food (ECI), efficiency of conversion of digested food (ECD), and relative growth rate (RGR) compared to those fed on the control diet. The highest relative consumption rate (RCR) was observed in larvae fed on the sunflower pollen-supplemented diet. Additionally, pollen-supplemented diets influenced the amylolytic and proteolytic enzyme activities of H. armigera larvae in a diet-dependent manner. Nutritional analysis of the pollen types revealed significant variations in the sugar, lipid, and protein contents. Cluster analysis further identified the date palm pollen-supplemented diet as the most nutritionally beneficial, suggesting its potential application in the large-scale production of H. armigera.

Spatiotemporal Patterns of Five Small Heat Shock Protein Genes in Hyphantria cunea in Response to Thermal Stress

Hyphantria cunea (Drury), a destructive polyphagous pest, has been spreading southward after invading northern China, which indicates that this insect species is facing a huge thermal challenge. Small heat shock proteins (sHSPs) function as ATP-independent molecular chaperones that protect insects from heat stress damage. In order to explore the role of sHSPs in the thermotolerance of H. cunea, five novel sHSP genes of H. cunea were cloned, including an orthologous gene (HcHSP21.4) and four species-specific sHSP genes (HcHSP18.9, HcHSP20.1, HcHSP21.5, and HcHSP29.8). Bioinformatics analysis showed that the proteins encoded by these five HcHSPs contained typical α-crystallin domains. Quantitative real-time PCR analysis revealed the ubiquitous expression of all HcHSPs across all developmental stages of H. cunea, with the highest expression levels in pupae and adults. Four species-specific HcHSPs were sensitive to high temperatures. The expression levels of HcHSPs were significantly up-regulated under heat stress and increased with increasing temperature. The expression levels of HcHSPs in eggs exhibited an initial up-regulation in response to a temperature of 40 °C. In other developmental stages, the transcription of HcHSPs was immediately up-regulated at 30 °C or 35 °C. HcHSPs transcripts were abundant in the cuticle before and after heat shock. The expression of HcHSP21.4 showed weak responses to heat stress and constitutive expression in the tissues tested. These results suggest that most of the HcHSPs are involved in high-temperature response and may also have functions in the normal development and reproduction of H. cunea.

Digestive Characteristics of Hyphantria cunea Larvae on Different Host Plants

Digestive physiology mediates the adaptation of phytophagous insects to host plants. In this study, the digestive characteristics of Hyphantria cunea larvae feeding preferences on different host plants were investigated. The results showed that the body weight, food utilization, and nutrient contents of H. cunea larvae feeding on the high-preference host plants were significantly higher than those feeding on the low-preference host plants. However, the activity of larval digestive enzymes in different host plants presented an opposite trend, as higher α-amylase or trypsin activity was observed in the group feeding on the low-preference host plants than that feeding on the high-preference host plants. Upon treatment of leaves with α-amylase and trypsin inhibitors, the body weight, food intake, food utilization rate, and food conversion rate of H. cunea larvae significantly decreased in all host plant groups. Furthermore, the H. cunea comprised highly adaptable compensatory mechanisms of digestion involving digestive enzymes and nutrient metabolism in response to digestive enzyme inhibitors. Taken together, digestive physiology mediates the adaptation of H. cunea to multiple host plants, and the compensatory effect of digestive physiology is an important counter-defense strategy implemented by H. cunea to resist plant defense factors, especially the insect digestive enzyme inhibitors.

Temperature- and Diet-Induced Plasticity of Growth and Digestive Enzymes Activity in Spongy Moth Larvae

Temperature and food quality are the most important environmental factors determining the performance of herbivorous insects. The objective of our study was to evaluate the responses of the spongy moth (formerly known as the gypsy moth) [Lymantria dispar L. (Lepidoptera: Erebidae)] to simultaneous variation in these two factors. From hatching to the fourth instar, larvae were exposed to three temperatures (19 °C, 23 °C, and 28 °C) and fed four artificial diets that differed in protein (P) and carbohydrate (C) content. Within each temperature regime, the effects of the nutrient content (P+C) and ratio (P:C) on development duration, larval mass, growth rate, and activities of digestive proteases, carbohydrases, and lipase were examined. It was found that temperature and food quality had a significant effect on the fitness-related traits and digestive physiology of the larvae. The greatest mass and highest growth rate were obtained at 28 °C on a high-protein low-carbohydrate diet. A homeostatic increase in activity was observed for total protease, trypsin, and amylase in response to low substrate levels in the diet. A significant modulation of overall enzyme activities in response to 28 °C was detected only with a low diet quality. A decrease in the nutrient content and P:C ratio only affected the coordination of enzyme activities at 28 °C, as indicated by the significantly altered correlation matrices. Multiple linear regression analysis showed that variation in fitness traits in response to different rearing conditions could be explained by variation in digestion. Our results contribute to the understanding of the role of digestive enzymes in post-ingestive nutrient balancing.