Study On Biological And Spatial Pattern Of A Scale Insect Coccus Sp.

Coccus sp. belongs to Coccus, Coccidea or Lecaniidea, Coccoidea,Homoptera. It is one of the main pest insect on the Leucaene glauca（L.）Benth. Thispest fed on the trunk and twig of the host plant that made the tree be withered andaffected existence and development of this tree directly.Earlier workers only studied the Aonidiella sotetsu(Takahashi) on the Leucaeneglauca（L.）Benth, but didn’t study the Coccus sp..Inquired information and investigated Leucaene glauca（L.）Benth in the fourmain growing areas in Yunnan Province from2008to2009. The result shows that thedistribution areas of Coccus sp. in Yunnan Province mainly are Dongchuan area,Qiaojia county and Yuanmou county.The investigation about damage was carried on in Dongchuan in2009. The dateshows: in different month, the damage percent and damage index is different. Thedamage percent between36.67%and85.33%and the damage index between15.56and50.22.Through fed Coccus sp. in lab in Kunming and observed it in Dongchuan from2009to2011, known life history and living habits of this pest in these two areas.Coccus sp. has4generations annually in the lab and has4-5generations annually inDongchuan, overlapping generations, not obvious over-wintering generation, the maininstars in the winter are1and2instar nymphs. In the lab, from May to September isthe period that the largest population density and the most serious damage, but inDongchuan from March to October is the period that the largest population densityand the most serious damage.The female adult was spawn eggs in the peritoneum. The hatching egg issuborbicular and the monocular is visible clearly.Nymph develop into adults by age2. The1instar has three growth stages:paralysis stage，active or distribute stage，fix or grow stage. The active stage can’t belonger76hours，average is18hours. The mortality in this stage is usually very high,in culture dish the mortality is40-70%，fixed rate is43.75%on the host plant. Theactive nymph physically crawl along the distance between16-67cm. Differentgeneration the1instar crawl difference distance. Generally the second and third generation of1instar nymphs more lively. Activity level of first and third generation1instar were reduced significantly.2instar fixed and feeding host by piercing-suckingmouthparts. Female adult was parthenogenetic, ovipary. In different generation, thefecundity of female is different, the eggs number between10and60and averagenumber is29.13.Before spawning, the female adult’s back was soft, graduallyhardening after spawning. A few hours later, the eggs hatch. The female adult’slifetime was7-25days. Female adult’s lifetime was also different in differentgeneration. The beginning of appearance, female adult’s color is light yellow, thencolor deepen gradually. Death female adult’s color was dark brown, without burnish.Extruded the back with anatomical needle, is is dry and no humoral. Didn’t find themale.In the2008and2009，investigated sampling plot in Dongchuan respectively withthe method of parallel lines and diagonal lines to analyzed the spatial pattern.The spatial pattern of Coccus sp. was determined, and the equations of optimalsampling are set up based on the regression models. Aggregated indices andregression analyses of Taylor’s Iwao’s and Lanxingping’s methods show that thespatial distribution patterns of Coccus sp. is aggregated distribution. In addition, theaggregation average method by Blackith was applied to analyze the aggregationreasons of the Coccus sp.. The spatial distribution pattern of the Coccus sp. waspositively related to its environment and the biological characteristics of itself. Amongthe4regression models, the Iwao model is the best one and the best equations ofsuccession sampling is d=5n±4.628n (n means sampling number).