Bactericidal substance induced in the haemolymph of Sarcophaga peregrina larvae

Bactericidal activity induced in the haemolymph of Sarcophaga peregrina larvae was investigated. It was found that this activity was due to a protein with a molecular weight of less than 10,000. The activity was lost on heating the haemolymph at 70°C for 5 min and it was dialyzable. This substance killed both E. coli and B. subtilis when incubated with them at 30°C, but not at 0°C. The possibility that this substance is lysozyme was excluded.