Mutualistic Association Between Lac Insect Kerria Yunnanensis And Ant Crematogaster Macaoensis

Lac insect is a kind of scale insect, parasiticing in host plants and draining plant fluids. Lac insect can secrete a kind of pure natural resin through glands——lac, lac as a kind of natural chemical raw materials, has important economic value. But in lac production, lac insect often suffered from predatory and parasitoids, leading to lac production decline. Lac insect secrete lac, and excrete honeydew meanwhile. Honeydew attracts ants visiting. To understand the effects of honeydew that lac insect Kerria yunnanensis excreted fed by ant Crematogaster macaoensis, on individual and population of C. macaoensis, and the effects of C. macaoensis on individual of K. yunnanensis, population dynamics, pest of K. yunnanensis and the lac production. The interactions between C. macaoensis and K. yunnanensis were studied from October 2008 to April 2011 in a lac plantation in Yayi region, Mojiang County, Yunnan Province, China, in this paper. The major results were as follows:(1)Crematogaster macaoensis monopolized the honeydew excreted by K. yunnanensis through the workers quantity advantage and constructed shelters. Crematogaster macaoensis fed and monopolized honeydews around the clock during the whole life cycle of K. yunnanensis on the stick-lac and the average numbers of visiting C. macaoensis ranged from 16.75±2.29 to 39.33±9.95 per 10 cm length of the stick-lac; C. macaoensis constructed shelters to prevent other animals from visiting the lac insects, but the number of workers were less than fifteen within every shelter, and the number of shelters constructed by each colony of C. macaoensis was less two, the way of C. macaoensis monopolized honeydew should represrnt a trade-off between the cost of C. macaoensis constructed shelters and the cost of lots of workers protected honeydew.(2)The honeydew of K. yunnanensis excreted was a kind of high quality food resources, and this honeydew could increased C. macaoensis workers'weight steadily, enhanced the survival rate of workers. Two mathematical models were established to predict C. macaoensis population dynamics, namely nest volume of C. macaoensis and the numbers of workers. The calculation formula were: V=0.365×( 4/3×πabc)^1.056, WN=135.236×V^0.660, respectively. ( Where V was the nest volume. a, b, c were long radius, short radius and extremely radius, respectively. WN was the numbers of workers.). With these two models, the numbers of workers monthly increasement in every nest could be estimated, by measuring the long radius, short radius and extremely radius of the nest. At last, the results suggested that the honeydew excreted by K. yunnanensis, could make the population of C. macaoensis develope and expand rapidly.(3)Crematogaster macaoensis monopolization honeydew significantly increased the percentage of K. yunnanensis'females and the adult female fecundity, reduced the population of the predatory and parasitic pests, and reduced the mortality of K. yunnanensis, had no significant effects on lac production by the whole lac insect colony; but C. macaoensis monopolization increased metabolic stress of K. yunnanensis, the specific performances were smaller body, less lac production per individual, and longer life cycle.(4)The relationship between ant C. macaoensis and lac insect K. yunnanensis associating with honeydew, is factulative mutualism.