| As an important pollinating insect of fruit trees in early spring in northern China,Osmia excavata Alfken,the pollination activity of the bees is susceptible to the adverse weather such as low temperature in early spring.In recent years,this artificial semi-domesticated bees has appeared the semiochemical of high natural abortion rate of eggs,high natural mortality rate of adults and very low reproduction rate.In order to cope with this situation,two kinds of artificial management measures were adopted: artificial release of semiochemical(bee activity enhancer)and artificial placement of nesting tubes of different sizes.This study explored the effects of semiochemical released artificially at flowering stage on the mason bees activity,fruit setting rate and apple fruit quality,as well as the effects of different sizes of nesting tubes(6,8,10 mm)on the sex distribution of O.excavata,so as to determine the most suitable size of nesting tubes for maintaining pollination of O.excavata population.The results are as follows:1.Effects of Artificial Release of Semiochemical on the Activity of O.excavata in Apple OrchardBy measuring the weight and cocoon length of female and male,it was proved that O.excavata had sex dimorphism of male and female.The dependence of apples on O.excavata for pollination was 0.95.The flower-visiting efficiency of bees in semiochemical treated orchards was 1.34 times higher than in control orchards,and releasing semiochemical significantly increased the fruit set of apples.Releasing semiochemical also increased mean apple weight by 3.53 g,and improved fruit quality by increasing the content of vitamin C by about 0.15 mg/100 g.2.Effects of Artificial Placement of Different Sizes of Nest Tubes on Sex Distribution of O.excavataBy measuring the weight and cocoon length of female and male bees,it was proved that the O.excavata has marked sex dimorphism.Adult females were 1.67 times heavier than males,and the length of female cocoons was 1.15 times that of male cocoons.By placing artificial nest tubes of different sizes,it was found that the parental investment increased with the increase of nest tube diameter.Increasing the inner diameter of the nest tube within acertain range can significantly increase the the number of female progeny,bee weight and cocoon length of the offspring.The sex allocation pattern of the O.excavata is that they give birth first to female and then to male.The proportion of female in the inner tube is the highest.With the passage of position,the proportion gradually decreases,and the proportion of male in the outer tube is the highest.During oviposition,there was a transition point from female to male,at which the ratio of female to male was equal to 0.5.The transition point gradually moved backward with the increase of cocoon number,and the ratio of cocoon length to total tube length increased significantly with the increase of cocoon number.In smaller diameter nest tubes,offspring tend to be male,whereas in larger diameter nest tubes offspring tend to be female.The available tube diameter can therefore affect bee weight,cocoon length and the sex ratio of progeny,and thereby the structure and stability of the local population.Changing the size of nest tubes can affect the size and sex ratio of offspring,providing a relatively simple way to optimize the management of this semi-domesticated,solitary bee species.The best nest tubes had an internal diameter in the range of 8-10 mm.The results showed that the O.excavata could improve the efficiency of pollinating insects visiting crops by releasing pheromones and other artificial management measures under low temperature and other adverse environmental conditions,thereby improving crop quality,increasing crop yield and reducing losses.Nest tube diameter affects the parental investment and sex ratio of O.excavata. |
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