Study Onkey Biological Characteristics Of Eucryptorrhynchus Chinensis (Olivier)

Eucryptorrhynchus chinensis (Olivier) is an important quarantine pest in many provinces in China, having strong host specialty of Ailanthus altissima (Mill.) Swingle and its variations. The weevil and its relative E. brandti (Harold) are easily confused both in prevention and researches. In this paper, researches published have been reviewed and some key biological characteristics had been observed and proper experiments were designed to figure them out. All the research results are as the follows.The adult weevils need nutritional supplement to reproduce. About 10%-20% adult weevils can oviposite small amout of eggs which cannot hatch into larvae. E. chinensis can reach its largest fecundity and hatching rate when fed with the material ofA. altissima, and seedling sprout and 2-3 years old branches are better choice as the feeding materials for the rearing of E. chinensis in laboratory.In natural condition, the female one would lay the eggs into the surface of the ground near the tree. Before laying eggs, the weevil would insert its snout into the soil for a few times and turn around its body to laying eggs. After the oviposition, it would cover the soil around to protect the eggs.The effect of the soil water content and whether there exist root were detected by the experiment with split block design. It showed that E. chinensis has abilities in adapting to the environment. The amount of eggs was correlated with the soil water content and the proper interval was 10%～20%. While the existing of root and its cross influence had no effect on the oviposition of weevils.According to the frequency of the width of larvae’s heads and tergums. it is proper to divide the larvae into six instars. And the width of head is a better index for instar division.The food consumptions were measured of the adults and the larvae of 6 instars. The consumption and the weight increased sharply during the 2nd ～3rd instar and 4th ～5th instars, while decreased during the 6th instar. The tunnels of larvae showed no regular shape. The width of the tunnels were near to the width of head. The tunnels of 1～2 instar were not visible in the field, while the tunnels of the larger instars were spiraling along the root.The complication of glue and soil can be seen as a signal for the damage caused by the larvae, also a result of the self-protection reaction. The component were detected and most of them are macromolecules alkanes.