The female Australian spider beetle may produce 120 or more eggs over 3-4 weeks in early summer. They are laid either singly or in batches and, being sticky, will adhere to the substrate. At 20-25'C the eggs hatch in 3-16 days, giving larvae which are fleshy, curved, covered with fine hairs and relatively immobile. although they will rapidly curl up when disturbed.
Development takes at least 6 weeks, during which time the larvae moult 4 or 5 times. When mature, they wander in search of a pupation site where they will spin a cocoon cell in which to pupate. These cocoons are often found on the outside of cartons through which the larvae have bored. Adults emerge after 20-30 days and will live for as long as 12 months. If disturbed they will feign death. The full life-cycle takes 3-6 months, depending upon ambient conditions, and can take place in a temperature range of 5-28'C. The life-cycle of the Golden spider beetle resembles that of the Australian species. The eggs hatch in 11 -30 days at 1 5-20'C, the larvae live for 150-250 days and pupation takes 18-26 days, after which the adults live for up to 8 months.
Gibbium psylloides again has a similar life-c, to the Australian and Golden spider beetles the adults are particularly long-lived, surviving for up to 1 1/2 years. The optimum temperature for development, which can take place within the range 20-35'C, is 33'C, when it takes about 45 days.
Gregarious and nocturnal, they spend the day in cracks and crevices amongst packaging and the fabric of the store. Consequently they can thrive in old buildings where they find many harbourages.