| There are millions of insects and plants widely distributed on the earth, the interaction relationships between insects and plants are extremely complicated, varying according to different species. Global warming, the general trend of present climate change, will certainly affect the life history and development of insects. Host plant is the most important biological factor, providing food source, habitats and breeding sites for leaf-feeding insects. Temperature is the most important abiotic factors, which directly affect the growth of leaf-feeding insects. Research on the interaction relationship between leaf-feeding insects and host plants and the response of leaf-feeding insects to temperature change will be very meaningful in both theoretical and practical aspects.In this study, we launched a series of research on Lemyra alikangensis (Lepidoptera:Arctiidae). Field investigations combined with the laboratory feeding experiments were used to study the life history of Lemyra alikangensi in subtropical evergreen broad-leaved forest, Tiantong national forest park, Zhejiang province. Using constant temperature illumination incubators to control the feeding conditions, the effects of different host plants to the feeding preference, development, fecundity and digestive enzymes activity of Lemyra alikangensi were studied. Temperature gradients were controlled through constant temperature illumination incubators, and the effects of temperature on feeding dynamics and development of Lemyra alikangensis larvae were studied. The results were summarized as below:1. Life history of Lemyra alikangensisLemyra alikangensis has three generations every year in Tiantong national forest park, Zhejiang. It has the overlapping of generations, with seven instars each generation. The first generation started in the late April and ended in the early July. The second generation was from late June to early September. And the third generation was from September to early May the next year, with a winter sleep. When the third generation larvae developed to6th instar (late October to early November), they would enter overwintering with the form of mature larvae. They started to develop at the end of March the next year, after having been ecdysised and became7th instar larvae, then followed the pupation and eclosion stages. The most serious period was from June to Auguest. In addition, the parasitism phenomena caused by tachinids was quiet commom in the wild, which could be used in biological control.2. Feeding preference of Lemyra alikangensis to different host plantsThe4th instar larvae of Lemyra alikangensis had significant feeding choice preference among five host plants. Clerodendrum cyrtophyllum Turcz had the highest feeding choice rate (45.00%), which was preferred most by Lemyra alikangensis. Ficus erecta Thunb. var. beecheyana (Hook. et Am.) King (18.67%) and Diospyros oleiera Cheng (17.00%) suffered the similar feeding choice rates. Camptotheca acuminate Decne (4.67%) and Myrica rubra (Lour.) Sieb. et Zucc (4.33%) had the lowest feeding choice rate, which indicated they were not preferred by Lemyra alikangensis.Lemyra alikangensis larvae also had significant food consumption difference among the five host plants. Individuals fed on M. rubra (3875.06mg) had the highest total food consumption, and those fed on Cl. cyrtophyllum (2977.51mg) had the lowest total food consumption. The daily average food consumption order was:M. rubra group (80.73mg/d)>d)>D. oleiera group (77.78mg/d)>Cl. Cyrtophyllum group (74.44mg/d)>F. beecheyana group (70.74mg/d)>Ca. acuminate group (70.43mg/d).In addition, the nutrition effects of different host plants on6th instar larvae were dramatically different. Generally, Cl. Cyrtophyllum group had the best nutrition effects, the indicators such as RGR (0.30mg.mg-1.d-1), ECD (13.46%) and AD (62.04%) were all the highest among all the groups. Ca. acuminate group was the worst. The indicators (RGR0.08mg.mg-.d-1, ECD4.39%, ECI21.81%, AD20.20%) were mostly the lowest among all the groups.In conclusion, we have confirmed Lemyra alikangensis’ feeding preference order: Cl. Cyrtophyllum>F. beecheyana>D. oleiera>Ca. acuminate>M. rubra.3. Effects of host plants on the development, fecundity and digestive enzymes activity of Lemyra alikangensisWhen Lemyra alikangensis were fed on five host plants, the indicators of Lemyra alikangensis, such as larvae duration, pupa duration, female pupa weight, fecundity, survival rate, amylase activity and trypsin activity in midgut, all displayed significant difference among different groups. There were negative correlations between larvae duration and survival rate, female pupa weight or fecundity. If Lemyra alikangensis had shorter larvae duration, the survival rate, female pupa weight and fecundity would be higher. On the other hand, if they had longer larvae duration, they would have lower survival rate, female pupa weight and fecundity. Amylase activity and trypsin activity in midgut were positively correlated to the development of Lemyra alikangensis. So the higher digestive enzyme activity, the better fitness between Lemyra alikangensis and the host plant.There were significant differences in nutrient contents among different host plants, and protein played more important role in the development of Lemyra alikangensis than total sugar, which indicated protein was most important in evaluation fitness between Lemyra alikangensis and host plant.In brief, Cl. cyrtophyllum was the most suitable host plant, while M. rubra was the least suitable one among the five host plants, this indicated M. rubra had the best defense characteristics among5host plants. Host plants’ nutrition ingredients, especially protein, could decide the feeding preference and development of Lemyra alikangensis, and the digestive enzymes could adjust the fitness between Lemyra alikangensis and host plant.4. Effects of temperature on feeding dynamics and development of Lemyra alikangensis larvaeFood consumption and development of Lemyra alikangensis (Strand) were studied under five constant temperatures (17,20,23,26,29℃). The results showed that temperature could significantly affect the food consumption amount and growth indicators of Lemyra alikangensis. Within the scope of the17～26℃, the larvae daily food consumption increased rapidly, larvae durations were significantly shortened and larvae survival rate increased significantly. In the temperature of29℃, however, the larvae daily food consumption began to decline, larvae duration began to extend and larvae survival rate also dropped. According to our theoretically calculation, Lemyra alikangensis larvae optimum feeding temperature was27.41℃, optimum growth temperature was26.48℃. In addition, the larvae development threshold temperature was6.91℃, effective accumulated temperature was720.71D·D. |
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