NEW MATERIAL:The compound of formula (X1 is Lys or Arg; X2 is Gly or Val; X3 is Leu or Ile; X4 is Ile or Val).

USE: An edible antibacterial agent.

PREPARATION: The body surface of a larva of an insect belonging to biptera or hymenoptera (e.g. Sarcophaga peregrina) is incised and the body fluid is squeezed out after about 2 days. The cells are removed by centrifugal separation, and the super- natant liquid is heated in water bath to remove the fat and centrifuged. The centrifuged supernatant liquid is treated with ion exchange resin, concentrated by ultrafiltration, and separated into constituent components by gel filtration, etc. After separating into each component, the component containing the objective compound is purified by properly combining an adsorption chromatography, electrophoresis, etc., to obtain the compound of formula.