| Synovigenic parasitoid refers to parasitoids with no or only few mature eggs in the ovaries of newly emerged females, thus female parasitoids have to feed on host food and/or non-host food to provide nutrient necessary for egg maturation and oviposition. Ovigey index (OI) is often used for estimating synovigenic degree of the parasitoids, i.e. the ratio of mature eggs in a newly emerged female to total eggs in its lifespan. In view that the resource utilization of female wasps of synovigenic parasitoids with hosts as food and that the host-feeding behavior have important significances in evolutionary ecology and in biological control, this project conducts studies on the important parasitoids of Liriomyza leafminers, i.e., Diglyphus isaea and Neochrysocharis formosa using the methods of experimental ecology, insect physiology, insect behavior etc. Firstly, the effect of female wasps of the two species feeding on host larvae on life history traits such as longevity and fecundity is studied, respectively. Then, the dynamics of nutrient absorption and metabolism after the female wasps of the single species feed on hosts is studied in order to clarify the nutritional and physiological mechanisms of host-feeding; meanwhile the correlation between the feeding and oviposition behaviors of female wasps and the inherent nutrient level wan analyzed to ascertain the ability of female wasps dealing with the variable resources. On this basis, the life history traits of the two species are compared, and the relationship between the synovigenic differentiation (Ovigey Index, OI) with the difference in life history traits, resource allocation strategies and nutrient utilization efficiency is established. The main results were listed as following:1. Structure of internal reproductive systems, ovarian development and oogenesis dynamics of the two parasitoidsThe structure of internal reproductive systems and developmental pattern of ovary in the two parasitoids were dissected and observed. The results showed that1) the internal reproductive systems of Diglyphus isaea Walker and Neochrysocharis formosa (Westwood) mainly contained a pair of ovary, two lateral oviducts, a common oviduct, a spermatheca, a mucous gland, a venom gland and a alkaline gland. In addition, there was a pair of accessory gland of median oviduct in female D. isaea. In general, the ovaries of both the two parasitoids were composed of6ovarian tubes, but difference was observed between individuals occasionally.2) The ovaries of both the two parasitoids were produced at the1st day after pupation. Ovarian tubes and egg-chamber were produced and vitellus began to be deposited in N. formosa at the3rd days after pupation, which were one day earlier than in D. isaea. No mature eggs were observed in newly emerged D. isaea females, thus it belongs to a high synovigenic parasitoid. However, some eggs has matured in newly emerged N. formosa females, so its synovigenic intension is weaker compared with D. isaea. Egg development could be accelerated when newly emerged female parasitoid fed on its hosts compared with clear water (control).2. Advantage of longevity and oogenesis of the two parasitoids feeding with host foods compared with feeding with non-host foodsThe longevity and oogenesis dynamics of the two parasitoids fed with hosts(Liriomyza sativae larvae), glucose, hosts plus glucose, distilled water were observed. The results showed that The results showed that1) The longevities of N. formosa females fed with hosts, glucose, hosts plus glucose, distilled water were20.2±1.6,34.6±1.9,23.9±2.1and3.3±0.2days, and the cumulant of mature eggs were139.2±1.5,36.8±0.4,134.9±1.6and5.2±0.3eggs/female within10days after emergence, respectively. After reabsorption of eggs, new mature eggs were produced at24hours after females re-fed on host larvae, but no new mature eggs were observed when the parasitoid fed on glucose.2) The longevities of N. formosa females fed with hosts, glucose, hosts plus glucose, distilled water were11.4±0.7,24.2±1.6,16.1±1.4and2.7±0.2days, and the cumulant of mature eggs were99.6±1.1,64.4±0.8,102.2±1.0and28.7±1.0eggs/female within10days after emergence, respectively. After reabsorption of eggs, new mature eggs were produced at12hours after females re-fed on host larvae, but no new mature eggs were observed when the parasitoid fed on glucose.3) Hosts and non-host foods can prolong significantly the longevities of the two parasitoids, and hosts can promote and enhance the number of more eggs. Although non-host foods can not promote oogenesis of the two parasitoids, glucose can postpone reabsorption of eggs. Differences in the longevity and oogenesis were observed between the two parasitoids, and the longevities of both the two parasitoids were extended, but total number of eggs in the two parasitoids was affected, when glucose were provided under the existence of host larvae. 3Effects of host feeding and non-host foods on contents of nutrient substances in the female adults of the two parasitoidsThe dynamics of nutrient indices in the female adults of the two parasitoids fed with host larvae, glucose, hosts plus glucose, distilled water were determined and compared. The results indicated that1) the glucosinolates and glycogen contents in the female adults of D. isaea fed with host larvae were significantly lower than those fed with non-host foods, but lipid contents fed with host larvae were higher than those fed with non-host foods.2) The fructose and glycogen contents in the female adults of N. formosa fed with host larvae were significantly lower than those fed with non-host foods, but lipid contents fed with host larvae were also higher than those fed with non-host foods.3) The lipid contents in D. isaea and N. formosa revealed a degressive trend, this demonstrates that the two parasitoids can't synthesize the substance.4. Effects of five common sugars on longevity and oogenesis of female adults of the two parasitoidsThe longevity and oogenesis dynamics of female adults of the two parasitoids fed with five common sugars in nature (glucose, fructose, sucrose, fucose and melezitos) were determined and compared. The results showed that1) the longevity of female D. isaea fed with monosaccharide was the longest, with the value of40.3±1.6days, and that fed with melezitos was the shortest, which was24.5±1.8days.2) For N. formosa female, the longest longevity was observed in the treatment of glucose, and the shortest was also noticed in the treatment of melezitos.3) Monosaccharide plays an important role in the longevities of both D. isaea and N. formosa, but there was a difference in the optimal adaption of monosaccharide to the parasitoids between the two parasitoids.5. Tolerance abilities of female adults of the two parasitoids to nutrient stressesThe longevity, capital and nutrition income dynamics of female adults of the two parasitoids were determined and compared under different nutrient stresses. The results revealed that1) there was a positive correlation between the body sizes of newly emerged adult parasitoids and their original capital nutrition, and the contents of glucosinolates and glycogen were the highest in the newly emerged D. isaea and N. formosa adults.2) The short-term nutrient stress did not affect significantly the longevities of D. isaea and N. formosa, but with the stress time was extended, the longevities of the two parasitoids were shortened sharply.3) Since the parasitoids could obtain foods to supply their nutrition, saccharides substances maintained a certain level in female adults when the nutrient stress produced. Since lipid was not synthesized in the parasitoids, its change was in accord with the longevity of female parasitoids.Base on the above results, both D. isaea and N. formosa are classic synovigenic parasitoids, and synovigenic degree of D. isaea is higher than that of N. formosa. The longevities of the two parasitoids were prolonged when they fed on host larvae and non-host foods and hosts can promote oogenesis. Although non-host foods can not promote oogenesis of the two parasitoids, glucose can postpone reabsorption of eggs. This is because lipid can't be synthesized in the two parasitoids, but oogenesis depends on lipid in nutrient substances, and the longevity only relies on carbohydrates in the adult parasitoids. The results/conclusions will enrich the evolutionary significance of host feeding behaviors in behavioral ecology of parasitoid, and provide a direction for the application of the parasitoids in biological control of pests.
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