Apanteles heterusias is the natural enemy insect that parasites in the larvae of mulberry pyralid (Diaphania pyloalis Walker). We have studied the parasitical rate of A. heterusiae for three years in succession by taking samples at random and at irregular time. The result shows that A. heterusiae is quite common in Suzhou region and its parasitical rate is very high, which ranges from 22.95 percent to 55.41 percent, with an average value of 33.99 percent and remains at a relatively high level during the year. The natural parasitical rate is the highest in the 5th generation in September, reaching 55.41 percent. Therefore, A . heterusiae is the preponderant natural enemy species and markedly controls the occurrence of mulberry pyralid ( D. pyloalis) and its damage. This paper reports the natural parasitical instance, the biological characteristics, and especially the ovipositing habit and the parthenogenesis of the adult and lays a foundation for the further implementation of the biocontrol of mulberry pyralid. Diaphania pyloalis (Pyralidae) : Host Apanteles heterusiae (Braconidae) : Parasite Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Land zones; Palaearctic region; Eurasia; Asia; China Apanteles heterusiae; Lepidopteran hosts; Parasite biology & prevalence; Diaphania pyloalis; Anhui; Suzhou region Diaphania pyloalis; Hymenopteran parasites; Parasite biology & prevalence; Apanteles heterusiae; Anhui; Suzhou region none