This paper describes Lissonota holcocerica Sheng sp.n. (Hymenoptera: Ichneumonidae), parasitizing Holcocerus hippophaecolus Hua, Chou, Fang and Chen (Lepidoptera: Cossidae) in Inner Mongolia, Liaoning, and Ningxia, China. The adults of L. holcocerica emerge from a cocoon during the daytime, mostly from 09:00 to 14:00 hr, then start calling and mating, mostly from 08:00 to 12:00 hr. Mating lasts from 15 sec to 15 min. The longevity of males is 5.8 ± 2.4 days, whereas for females longevity is 7.6 ± 4.6 days in the field. Nutritional supplements can significantly extend the life span of L. holcocerica. Mated females search for hosts by walking on the base of Hippophae rhamnoides L. (Rosales: Elaeagnaceae) stem infested by Ho. hippophaecolus, vibrating their antennae and tapping while searching the stem for oviposition sites. Parasitized cocoons of Ho. hippophaecolus collected in field were half the size of normal ones or even smaller.