The insects of the subfamily Bruchinae are known as seed beetles or weevils. The species Pachymerus nucleorum (Fabricius) attacks different vegetal species, among them the babassu palm (Orbygnia). The study of ATPases (enzymes that hydrolise ATP to produce cellular work) of insects have been widely researched. A fraction with high Ca²⁺-ATPase activity was obtained from Pachymerus nucleorum larvae. The larvae were dissected and their digestive system removed, while the remainder of the body was homogenized in extraction buffer and centrifuged at 15000_xg for 30 min. The resulting precipitate (P1 fraction) was homogenized in Imidazol buffer containing 0.2% Triton X-100, incubated for 20 min at room temperature and centrifuged under the aforementioned conditions. The precipitate (P2 fraction) was homogenized in Imidazol buffer containing 50 mM of pyrophosphate and centrifuged at 40,000_xg for 30 min, resulting the P3 precipitate (ATPase fraction). The ATPase activity was dosed by quantifying the inorganic orthophosphate released during the hydrolysis reaction of the substrate. The P3 fraction presented high Ca²⁺-ATPase activity but no Mg²⁺-ATPase activity nor any activity in the presence of other bivalent cations (cobalt, copper, zinc, barium, lithium and iron). The Ca²⁺-ATPase activity was inhibited by other bivalent cations, with 0.25 mM magnesium causing inhibition of 50% of this activity. In the presence of 1 mM ATP, the ATPase activity attained 50% with 0.5 mM CaCl₂, reaching a plateau at approximately 2 mM. In 1 mM of CaCl₂, the ATPase activity reached 50% of activity with 0.7 mM of ATP, reaching its peak at 2 mM and declining markedly thereafter. The P3 fraction did not use as substrates pyrophosphate nor mono- or diphosphate nucleotides, and the Ca²⁺-GTPase activity was only 20% that of the Ca²⁺-ATPase. This fraction did not undergo significant inhibition by vanadate at concentrations below 200 µM, 1 or 10 mM azide, 0.2 or 0.8% Triton X-100 or aluminum fluoride. Significant K⁺/EDTA-ATPase activity was observed (50% of the Ca²⁺-ATPase), suggesting the presence of myosins in this fraction. In this study we obtained a Ca²⁺-ATPase activity-rich fraction from Pachymerus nucleorum larvae without digestive system and partially characterized this activity.