Studies On Differentiation Comparison Of Different Geographic Populations In Chrysomya Megacephala(Fabricius)

Chrysomya megacephala (Fabricius) is a cosmopolitan synanthropic insect and closely connects with human health. On the one hand, it has been used in forensic entomology for obtaining biological evidence. On the other hand, Chrysomya megacephala is an important insect resource. We have collected Chrysomya megacephala from 6 different provinces,such as Wuhan, Hubei province, Changsha, Hunan province, Nanchang, Jiangxi province, Hangzhou, Zhejiang province, Zhangzhou, Fujian province, Zhuhai and Guangdong province.Some morphological and biological indexes and development time and size-related traits along a latitudinal gradient of Chrysomya megacephala collected from 6 different geographical populations had been compared. The main results are as follows:1. MorphologySome morphological indexes of each instar (egg, maggot, pupa and adult) of 6 different geographical populations were compared. The results showed that there were significant differences among others in each index. The body length and body weight of the maggot and pupa were important factors for forensic entomology. The populations from Fujian,Guangdong and Zhejiang were significantly different among others in body length and body weight of maggot during 1-day-old and 3-day-old, while the populations from Fujian,Guangdong and Zhejiang were significantly different among others in body length and body weight of maggot during 1-day-old and 3-day-old. There were significant differences among others in pupa length. The pupa length of Hubei population was the maxmum, while the pupa length of Zhejiang population was the minimum. The harvest time was another important factor to affect the yield of maggot for a insect resource. The results showed that the body length and body weight peaked when the larva was 4.5-day-old and then, with the passage of time, both indexes decreased. So in order to obtain high yields, the harvest time was the 4.5-day-old maggot.2. BiologyThe biological characteristics of 6 different geographical populations were compared in this article. The results showed that development durations of the egg and pupa of different geographical populations were significantly different among others. The egg development duration of Jiangxi population was the longest, while the egg development duration of Fujian population was the shortest. The pupa development duration of Guangdong population was the longest, while the pupa development duration of Jiangxi population was the shortest. There was not significant difference among others in maggot development duration, but the first, second and third instar maggot development durations of different geographical populations were significantly different among others, which had a certain refence value to accurately infer the time of death. The indexes of cold hardness like supercooling point(SCP) and freezing point in each instar (maggot, pupa and adult) of different geographical populations were significantly different among others. The highest SCP of maggot, pupa and adult belonged to Fujian, Hubei and Jiangxi population, while the lowest SCP of maggot, pupa and adult belonged to Guangdong, Hunan and Zhejiang population.3. Development time and size-related traits along a latitudinal gradientThe development time and size-related traits along a latitudinal gradient of 6 different geographical populations were compared in this article.Body size (body length and body width) of both males and females increased with temperature inconsistent with the general pattern in ectothermic animals. Blowflies took shorter to develop at higher temperature. Pre-adult survivorship was higher at high (30℃) temperature than at low (20℃) temperature. The response to temperature differed considerably among populations for body length, body width and development time, indicating genetic differentiation among populations in thermal reaction norms; There were weak differences among the three populations for pre-adult survivorship. There is no apparent trade-off association between developmental time and body size (body length and body width) across our set of populations, though for female, the trade-off association between Hunan population (the higher latitude,28.21°N) and Fujian population (the lower latitude, 24.52°N), with Hunan population developing slower but being bigger than Fujian population.