| Chrysomyces megacephala(Fabricius)is a holometabolous insect species,belonging to Order Diptera,Family Calliphoridae,and Genus Chrysomya.It Widely distribute in tropical and subtropical regions.The larvae are abundant in protein and fat,making them a potential alternative protein source to fishmeal.With its significant diet resource value,it holds promising applications in feed industry.However,collecting Chrysomyces megacephala in natural environments is challenging,and it is known to carry various pathogens.By employing artificial rearing methods,it becomes possible to obtain a large number of individuals while controlling the spread of pathogens.Currently,there is limited research on large-scale artificial rearing of the Chrysomyces megacephala.In order to understand the key factors involved in its large-scale rearing and determine the optimal ecological conditions for artificial rearing,this study utilized an orthogonal experimental design to optimize a practical formula for the artificial diet of Chrysomyces megacephala larvae and employed this formula to rear experimental populations over multiple generations.The effects of the formula on the growth and development of Chrysomyces megacephala were evaluated.In addition,the feeding behavior of Chrysomyces megacephala on the artificial diet was observed under various temperature conditions,including both variable and constant temperatures.The results of the study are as follows:1.In the experiment to optimize the practical formula for the artificial diet of Chrysomyces megacephala,there were no significant differences in terms of survival rate(F= 2.200,P = 0.189),pupal weight(F = 1.880,P = 0.219),eclosion rate(F = 0.101,P = 0.762),female duration(F = 1.109,P = 0.352),egg number(F = 0.042,P = 0.845),and hatching rate(F = 0.044,P = 0.841)compared to the control group fed on pork.However,the optimized formula showed significantly better results than pork dieting in terms of larval development period(F = 7.500,P = 0.034),pupa duration(F = 7.500,P = 0.034),pre-oviposition period(F= 23.420,P = 0.003),and oviposition period(F = 8.652,P = 0.026).2.The results of successive generations rearing showed that the female adult lifespan from the 1st to the 5th generation in the population fed with artificial diet was relatively longer,all exceeding the control group(F = 14.547,P < 0.001).There was a significant difference in egg-laying amount between the population fed with artificial diet and the control group(F = 3.048,P = 0.028).The oviposition period from the 1st to the 5th generation in the population fed with artificial diet was significantly higher than the control group(F = 14.547,P < 0.001).The remaining ecological parameters of the population fed with artificial diet showed no significant differences compared to the control group and were similar to or even better than those fed with natural diet.The average number of eggs laid per female reached366.5 after rearing up to the 9th generation,which was higher than the control group’s average of 349.0 eggs.3.Through indoor rearing Chrysomyces megacephala in the Haikou area indicated that egg stage lasting from 8 to 22 hours,larval stage lasting from 5 to 9 days,pupation occurring within 3 to 6 days.The adult stage varied from 30 to 110 days.The species could reproduce at least 13 generations per year,with a significant overlap of generations and no overwintering phenomenon.The activity of Chrysomyces megacephala adults was greatly influenced by temperatures.During warmer months,adults exhibited higher activity,increased oviposition potential,and higher egg viability.Adult females tended to aggregate for oviposition,with an average egg-laying amountapproximate to 300 eggs.The egg hatching period shorten with increasing temperatures,and higher temperatures resulted in better hatching rates during warmer months.Larval survival and eclosion rates were higher in relatively cooler months compared to relatively warmer months,with no significant differences in pupation rates throughout the year.The sex ratio was approximately 1:1 throughout the year,and pupal weight varied among different months without clear patterns.4.Under constant temperature conditions,there were significant differences in hatching rate(F = 30.061,P < 0.001),larval survival rate(F = 19.745,P < 0.001),pupation rate(F =17.740,P < 0.001),eclosion rate(F = 28.187,P < 0.001),pupal weight(F = 15.324,P <0.001),and sex ratio(F = 3.330,P = 0.039).The egg period(F = 1294.685,P < 0.001),larval period(F = 414.748,P < 0.001),pupal period(F = 273.465,P < 0.001),and total larval period(F = 615.256,P < 0.001)all shortened significantly as temperature increased.The developmental rate well fited to the Logistic model with temperature variations.Under constant temperature conditions,the developmental threshold temperatures for eggs,larvae,pupae,and the entire larval period were 10.72°C,10.57°C,8.85°C,and 9.82°C,respectively.The effective accumulated temperatures were 196.98(degree·hours),2469.11(degree·hours),2168.89(degree·hours),and 4853.19(degree·hours),respectively.Under indoor variable temperature conditions,the developmental threshold temperatures for eggs,larvae,pupae,and the entire larval period were 12.16°C,11.15°C,8.55°C,and 9.52°C,respectively.The effective accumulated temperatures for eggs,larvae,pupae,and the entire larval period were175.20(degree·hours),2389.64(degree·hours),1785.24(degree·hours),and 4565.99(degree·hours),respectively.5.The life table analysis showed that the life expectancy values of Chrysomyces megacephala decreased significantly with age.Under constant temperature conditions,25°C was the optimal temperature for the growth,development,and reproduction of Chrysomyces megacephala population.The life expectancy values for eggs,larvae,and pupae were 2.25,1.83,and 1.40,respectively,at this temperature,and the population trend index was up to the highest 60.63.By establishing a successive life table under indoor variable temperature conditions,it was found that temperature,food,and rearing techniques were important factors affecting the growth,development,and reproduction of the artificially reared Chrysomyces megacephala population.In conclusion,Chrysomyces megacephala can complete its entire life cycle when fed with optimized artificial diet under constant temperature conditions of 20°C,25°C,and 30°C,as well as under indoor natural variable temperature conditions(19～32°C).The ecological characteristics of the population fed with artificial diet are similar to or even better than those fed with natural diet.This indicates that the optimized formula can be used for long-term rearing of Chrysomyces megacephala.It demonstrates the feasibility of using this artificial diet to rear Chrysomyces megacephala in the Haikou area and can save energy and resources required to establish rearing systems in other places,making large-scale rearing and resource utilization of Chrysomyces megacephala a reality. |
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