The reasons are natural environment and food sources.

1. Natural environment: Xuancheng is located in Jianghuai Plain, with humid climate and abundant vegetation, which is a suitable environment for insect reproduction. There are lakes, rivers, farmland, etc. around the campus, which provide conditions for insects to reproduce and survive.

2. Food source: Insects usually feed on plants, and lawns, gardens and vegetated areas in the campus provide rich food sources, attracting insects to gather.