To investigate the current situation of the insect resources of Populus euphratica forest in Ejina and analyze the diversity of insect community in order to provide ecological basis for establishing the data base of the insect resources and protecting the P. euphratica forest in Ejina. From May to July 2023, the insect community structure and diversity of natural and different disturbance types of P. euphratica forest in Ejina were investigated and analyzed by using color plate method, Malaise net method, lamp lure method, sweeping net method and sweet and sour solution method. The results showed that a total of 182 973 insect specimens were collected, belonging to 12 orders, 170 families, and 793 species. Hemiptera, Diptera, Hymenoptera, and Coleoptera were the dominant groups, and the number of Diptera individuals was far greater than that of other orders, accounting for 52.434% of the total number of individuals, followed by Hemiptera at 21.134%. In the natural P. euphratica forest, the dominant groups in terms of individual numbers are Hemiptera and Diptera, the number of insect individuals showed the following order: Over-mature forest > young forest > middle forest > declining forest, the Shannon-Wiener diversity index (H′) was the largest in the middle forest, and the Margalef richness index (dM) was the largest in the Declining forest, the insect diversity index was the lowest in May, the number of phytophagous insects (16 752) and predatory insects (6 854) was the largest in the young forest. In the P. euphratica forests with different disturbance types, the dominant groups in terms of individual numbers were Hemiptera and Diptera, the number of insect individuals showed the following order: Grazing area P. euphratica forest > Tourist area P. euphratica forest > Farmland area P. euphratica forest, the Shannon-Wiener diversity index (H′) and the Margalef richness index (dM) were the largest in the Grazing area P. euphratica forest, the insect diversity index was the lowest in May, the number of phytophagous insects (7 846) and predatory insects (4 664) was the largest in the Grazing area P. euphratica forest. The results preliminarily revealed the diversity of insect species, quantity and community in P. euphratica forest, and provided ecological basis for further management of P. euphratica forest and pest control by understanding the dynamic changes of insect community in real time.

Xylotrechus namanganensis Heyden is an important wood-boring pest of Populus euphratica Oliv, Ulmus pumila L and other broad-leaved trees, and it was included in the "List of Dangerous Pests in Forestry" by the State Forestry Administration in 2013. It is very difficult to classify the instar of the larvae because it is extremely cryptic.In this study, the larvae of X. namanganensis were collected periodically from P. euphratica forests in Ejina at different developmental stages, and five morphological indexes of their body length, body width, head capsule width, distance between antennal rings, prothoracic plate width were selected. Frequency distribution diagrams were used to determine the preliminary larval instars numbers, and Crosby's rules and regression analysis were used to verify the analysis. The results showed that the larvae of X. namanganensis could be divided into six instars. The body width, head capsule width, distance between antennal rings, prothoracic plate width, all of which conformed to Dyar's. There was a significant fitting relationship between the measured values and larval instars numbers. Among them the fit between the width of the anterior thoracic dorsal plate (Y) and the age of the larva (X) was the highest, and the regression equation was Y=0.5192e^0.3782x (r²=0.9667), which was the best indicator for larval instar classifications. This article has certain guiding value for the study of the occurrence pattern and bioecological characteristics of X. namanganensis, the development of control strategies and prediction and forecasting of the occurrence pattern of the pest, and it also provides experience for the protection of rare P. euphratica forests in other regions.