Subtropical organisms are characterized by discriminating elemental profiling at P-rich and P-deficient sites. Elemental imbalance generally presents between parasite and their resources. But little has been reported on the parasite homeostasis regulation and the body size variation of parasite in response to the hosts, especially, at P-rich and P-deficient sites. To reveal these, we detected the content of 15 elements (C, N, H, O, P, K, Ca, Mg, Fe, S, Al, Mn, Na, Zn and Cu) in acorns of Quercus variabilis, in their parasitic weevil (Curculio davidi) larvae, and in weevil larvae feces at P-rich and P-deficient sites in subtropical China. Weevil larvae N and Cu were significant different in acorns at P-rich and P-deficient sites. At both sites, weevil larvae presented high uptake rate and low release rate for N and Zn, while showed low uptake rate and high release rate for O, K, Ca, and Mn. Although no significant relation presented in size of weevil larvae and acorns at two sites, weevil larvae weight increased with acorn N content and decreased with acorn Mn content, and weevil weight decreased with weevil Mn content (no relation to other nutrients) across P-rich and P-deficient sites. Moreover, acorns, weevils and feces could be discriminated at P-rich and P-deficient sites, with N as one of the major contributors. These results suggested that parasitic insects have formed distinctive nutrient usage models via the post-ingestion to maintain the somatic element balance, related to the discriminating host nutrient models at P-rich and P-deficient sites; acorn nutrients played vital roles on the regulation of weevil larvae growth, not acorn space; the N requirement of weevil larvae at P-deficient sites was more than these at P-rich sites due to the long-term adaption to acorns of variation nutrients.