| Cotton aphid Aphis gossypii (Homoptera: Aphididae), an important agricultural pest, its distribution extends from 60 N to 40 S in the world. This insect is capable to survive under different climatic conditions due to its wider adaptability. In summer, this insect reproduces parthenogenetically from generation to generation, after the late autumn it produces sexual aphids to lay eggs to over-winter. This paper presents studies on ecological adaptability of Aphis gossypii under different temperature and photoperiod ranges in the laboratory.Adults of Aphis gossypii were collected from cotton plants in Ho Chi Minh city of Vietnam (106.42 E, 10.45 N), Beijing (116.5 E, 39.9 N), Shihezi city of Xinjiang Municipality (85 E, 45 N) and Sanya city of Hainan Province (109.5 E, 18.2 N) in 2001 and these adult populations were named as YN, BJ, XJ and HN respectively. Each aphid culture was maintained on cotton seedlings at 22 C, 70%RH, and a photoperiod of 14:10 (L:D). The morphological variation of growth and development and relationship between emergence of sexual morphs and photoperiod (L:D=8:16 and L:D=10:14) at 18 C as well as the life parameters of these populations at different temperatures were evaluated.In the 1st part of the study with asexual aphids, fifty aphids from each of the 4 populations (i.e. YN, HN, BJ and XJ) were placed at various temperatures (15, 20, 25, 30 and 35 C respectively) maintaining 70%RH, and photoperiod L:D=16:8. Each aphid from respective population was fed on cotton cotyledon in 25ml glass beaker with 10ml-dissolved medium at the bottom. The newly produced aphids were transferred on cotyledon, and the cotton cotyledon was put on the surface of culture medium tightly. The newly produced nymphs were picked out everyday, but the adults were allowed to remain in the same container with replacement of fresh cotyledon and medium as and when required (Leaf Wafer Method). In the experiment, forty newly produced nymphs and the dead adults were all kept. Morphological parameters, such as foreleg femur length, foreleg tibia length, midleg femur length, midleg tibia length, hindleg femur length, hindleg tibia length, body length and body width were studied.In the 2nd part of the study with sexual aphids (collected from cotton plants), forty 4th instar aphids (G0) were transferred into environment chamber and allowed to breed using LWM. After 24 hours, the G0 adult aphids were removed, and forty new nymphs (G1) from G0 generation were introduced to breed until generation three (G3). The G2 nymphs were kept on feeding, which were produced at the 2nd, 7th, 12th and 17th day separately. During the growth period, the number of apteral and alate aphids was checked and the alate ones were transferred to cotton plants having 3 to 4 leaves to get G3 generation. The cotton plants were enclosed with transparent plastic sleeves, which were covered at the top with gauze. The ratesof development of three types of aphids (1) virginoparae cotton aphid in G3 with reproductive potential, (2) male alate aphid with genetalia without reproductive potential and, (3) female apteral aphid having eggs ] were observed.In the 3rd part of the study, fifty aphids from each of the 3 populations (i.e. YN, BJ and XJ) were placed at various temperatures (15, 20, 25, 30 and 35 C respectively) maintaining 70%RH, and photoperiod L:D=16:8. Each aphid from respective population was breed with LWM. Ecdysis, reproduction and death of aphid were observed everyday until all aphid adults died.The results showed that there were significant differences of morphology and color while they developed under various temperatures. Length of foreleg femur, foreleg tibia, midleg femur, midleg tibia, hindleg femur and hindleg tibia, head width and cornicles length of aphid from HN showed significant differences with those from BJ and XJ population. The surface area of both adult and larval aphids gradually increased with decreased temperature. It was found that there were also observed significant differences in surface area among Y...
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