2013, 26(6): 786-789.
In recent years, Agrilus mali Matsumura has outbroken in the Xinjiang wild fruit forest, and become the primary threat to Malus sieversii. In early study, the larvae of Agrilus mali were divided into six instars. However, the particular reason and method were not mentioned, and the larvae of Genus Agrilus were usually divided into four or five instars. For better pest forecasting and control strategies, the determination of larval instars was studied again. A.mali larvae were sampled periodically in forest, and the eggs were collected to hatch the first instar larvae. Three characteristics (i. e. peristoma width, urogomphus length and body length) were measured by binocular microscope with an eyepiece micrometer. According to the Dyar's law, the data were managed with frequency analysis, and examined by one-way ANOVA method, Crosby ratio and checked with larvae which were molting when sampling. The results showed that, the A. mali larva has five instars, and all three determination characteristics are effective except body length.