Chitin injection into closed pitchers induced changes in protein pattern and chitinase activity of pitcher liquid. Colloidal chitin (1 mg) was injected into closed young traps. (A) General protein pattern of the trap liquid: liquid samples (100 μl) taken prior to injection (lane 1) and 4 d (lane 2) or 8 d (lane 3) after injection were separated on a 12% SDS–polyacrylamide gel and subsequently stained with a silver stain. Arrows indicate chitin-induced bands, dots indicate chitin-enhanced bands. (B) Chitinase activity estimated on a native gel: samples (30 μl) taken prior to injection (lane 1) and 20 h (lane 2) or 5 d (lane 3) after injection. Following electrophoresis, the gel was overlaid with an additional gel containing 0.01% (w/v) glycol-chitin and assayed for chitinase activity. Arrows show induced chitinase bands and the dot shows the chitin-enhanced band.