Laboratory investigation was carried out on e instar larvae of Spodoptera littoralis tissues which treated with precocenes, insect path­ogenic nematode or precocenes-nematodes complex in order to clarify the infectivity of nematodes, mortality of S. littoralis larvae, the survival rate of nematodes infective juveniles (IJ) and energy consumption of the metabolic pathways, established in reserve materials of S. littoralis lar­vae. The obtained results of nematode-precocene combinations exhibit ed that larvae treated with 40 jig and 25 pg (Ph-N) suffered mortality, reaching to 92% and 157.14%, respectively, compared to precocene treatment atone. This may due to enhanced infection by the nematode. This lethal effect was most probably caused by stressing metabolites, then blocking the process of their role in the self-defense, through me­tabolites targeting. A protein depression of about 81.57% was found in the larvae treated with 40 pg (Pl+N) and of about 74.31% in those treated with with 25 pg (Pl+N) compared to control treatment.