Abstract: Entomopathogenic nematodes are cultured in a culture vessel comprising a tray with side walls and an overlapping lid, also with side walls. A gasket of polyether polyurethane foam is positioned around the inside edge of the lid, preferably in a gutter formed by the walls of the lid and inclined flanges attached to the lid. Preferably the lid has apertures in it, closed with resilient seals. Stop members, mounted on the inside faces of the walls of the tray, prevent forced movement of the lid towards the tray when the flanges bear against the stop members, thus enabling the culture vessels to be stacked on each other without over-compression of the foam gasket. A method of rearing nematodes using such a culture vessel involves coating a layer of crumbed foam in the tray with an offal homogenate, closing the culture vessel, autoclaving it, inoculating the coated foam with the appropriate symbiotic bacterium, incubating this bacteria at about 23.degree. C.