Improved insect cell lines, two of which are designated H5CL-B and H5CL-F (both of which are derived from the parental cell line BTI-TN-5B1-4, ATCC CRL 10859), possess the properties of increased production of baculovirus particles, increased expression of foreign proteins using a baculovirus expression system, and increased resistance to cell culture stress, relative to the parental cell line.