【摘要】 <正> 一、序言蓖麻蚕(Philosamia cynthia ricini)是属于鳞翅目天蚕蛾科(Saturniidae)的绢丝见虫,原产印度。一年可发生七、八代,在发生的任何阶段中都不休眠。根据蓖麻蚕的幼虫皮斑和血色,中国科学院实验生物研究所数年来已选育出五个定型种:即素白型、姬黄型、蓝皮型、花白型和花黄型。樗蚕(Philosamia cynthia)和蓖麻蚕的血缘很近,野生,喜吃臭椿和乌桕的叶子,以蛹越冬。樗蚕的地理分布范围很广,所以有许多地理上的亚种,化性和更多还原

【Abstract】 According to the differences in the larval skin colors,presence or absence of black spots on the cuticle and the colors of the blood,Philosamia cynthia ricini may be dis- tinguished into several different types.As a result of the crosses of the five different types of P.c.ricini,it was found that the blue skin is dominant over the white skin,black spots on the cuticle dominant over the absence of the black spots and the yellow blood dominant over the white blood.The result further shows that the larval patterns of P.c.ricini appear to be governed by three different pairs of genes,each of which is ap- parently located on a separated chromosome.Hence,in F₂ and the backcrosses,the re- combinations of these three pairs of genes give to eight different types of larval skins in due proportions.Philosamia cynthia Walkeri,another subspecies of P.cynthia,is a kind of wild silkworm.There are several characters which distinguish P.c.Walkeri from P.c. ricini.From the results of the crosses of P.c.Walkeri and P.c.ricini,it was found that the green skin of P.c.Walkeri is dominant over the blue and white skin of P.c.ricini, the small spots on the cuticle of P.c.Walkeri dominant over the absence of the black spots of P.c.ricini,but the small spots on the cuticle of P.c.Walkeri is recessive to the large spots on the cuticle of P.c.ricini.The cocoon color of P.c.Walkeri is greyish yellow,and that of P.c.ricini is white but the F₁ hybrids between them show a brownish red color,and the F₂ give cocoons with a variety of colorations varying in a continuous fashion.When the F₁ individuals were backcrossed to P.c.ricini,the cocoon colors seg- regated in a ratio of 1:1,which suggests that the difference in cocoon color between P.c.Walkeri and P.c.rinici seems to be controlled by one pair of gene.When the gene blue skin is combined with the gene yellow blood,the skin color of larvae appears to be green.When the gene white skin is combined with the gene yellow blood,the skin color of larvae appears to be yellow.The pupae of F₁ and F₂ did not diapause. Cytological examinations show that the diploid chromosome number of P.c.ricini is: 28,and that of P.c.Walkeri is 26.In the primary spermatocyte of F₁ of the cross P.c. Walkeri×P.c.ricini,12 bivalent and 1 trivalent chromosomes were observed.This suggests that in the course of evolution of P.c.ricini from the related wild,P.c.Walkeri, one pair of chromosomes in the latter could have been separated into 2 pairs of chromo- somes in the former.An additive evidence in favour of the above suggestion is the fact that whereas the chromosome number of P.c.Walkeri collected from Shanghai,Shan- tung or Lianning is 26,at least one geographical strain of P.c.Walkeri collected from Wenchow,Chekiang Province,show 28 chromosomes,among which two are distinctly smaller than the rest.更多还原