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This study aims to investigate the developmental interactions of <i>Asecodes hispinarum</i> Bouček on <i>Brontispa longissima</i> Gestro and <i>Octodonta nipae</i> Maulik, as well as the cellular immune responses of <i>B. longissima</i> and <i>O. nipae</i> larvae in response to parasitism by <i>A. hispinarum</i>, with the hope of determining the reason for the difference in larval breeding of <i>A. hispinarum</i> in <i>B. longissima</i> and <i>O. nipae</i>. The effects of parasitism by <i>A. hispinarum</i> on the larval development, hemocyte count, and proportion of the hemocyte composition of the two hosts were carried out through selective assay and non-selective assay using statistical analysis and anatomical imaging. There was no significant difference in parasitic selection for <i>A. hispinarum</i> on the larvae of these two beetles; however, more eggs were laid to <i>B. longissima</i> larvae than to <i>O. nipae</i> larvae after parasitism by <i>A. hispinarum</i>. The eggs of <i>A. hispinarum</i> were able to grow and develop normally inside the larvae of <i>B. longissima</i>, and the parasitism caused the larvae of <i>B. longissima</i> become rigid within 7 d, with a high larval mortality rate of 98.88%. In contrast, the eggs of <i>A. hispinarum</i> were not able to develop normally inside the <i>O. nipae</i> larvae, with a high encapsulation rate of 99.05%. In addition, the parasitism by <i>A. hispinarum</i> caused a 15.31% mortality rate in <i>O. nipae</i> larvae and prolonged the larval stage by 5 d and the pupal stage by 1 d. The number of hemocytes during the 12, 24, 48, 72, and 96 h of the four instars from <i>O. nipae</i> larvae was 6.08 times higher than from <i>B. longissima</i> larvae of the same age. After 24 h of being parasitized by <i>A. hispinarum</i>, the total number of hemocytes and granulocyte proportion of <i>B. longissima</i> larvae increased significantly. However, the total number of hemocytes and plasmatocyte proportion of <i>O. nipae</i> increased significantly after 24, 72, and 96 h, and the proportion of granulocytes increased significantly after 12 h post-parasitism. The results in the present study indicated that <i>A. hispinarum</i> was unable to successfully reproduce offspring in <i>O. nipae</i>, but its spawning behavior had an adverse effect on the larval development of its host. In addition, the adequate number of hemocytes and more pronounced changes in the hemocyte count and hemocyte composition ratio in the larvae after parasitization may be important factors for the successful encapsulation in <i>O. nipae</i> larvae.