Abstract: A diet for mass rearing of insects that feed on hard, woody plant tissue, e.g., beetles including weevils that feed on hard, woody plant tissue, comprises a homogeneous mixture of first portion which is subjected to sterilization in an autoclave comprising water, agar and salt mix and optionally also yeast extract, casein and a sugar, and of a second portion which is not subjected to sterilization in an autoclave which comprises host plant part fed on by insect larvae, vitamin mix, and antimicrobial agent(s). A method for mass rearing of insects that feed on hard, woody plant tissue, e.g., weevils, e.g., Hylobius transversovittatus or Cyphocleonos achates Fahraeus, comprises placing first instar insect larvae on an artificial diet comprising ground host plant part, incubating the larvae on the diet in darkness at a temperature ranging from 15 to 30° C. and a relative humidity ranging from 50 to 90%, and retrieving adults as they emerge.