Brown Recluse Spider Biology

Female brown recluse spiders weave off-white, silky egg sacs to lay their eggs in. They will construct up to five egg sacs and deposit about 40 to 50 eggs in each. The sac is loosely woven and measures approximately 2/3″ in diameter. Females tend to lay their eggs from about May to July.

It takes roughly a month for young spiders to emerge from their egg sac. These newly hatched spiders are known as spiderlings. The young spiders molt (shed their skin) one time within the egg sac and then several times after emerging. The period of time between molts is known as an instar. A brown recluse will go through eight instars total. The spiderlings will stay with their mother through the first three or four instars, during which time she provides them with prey. After that, the spiders tend to disperse.

Development into adulthood can be slow, depending on the availability of food as well as the weather. However, in general, a brown recluse's development from egg to adulthood is about one year.

Adults typically live for a year or two, but it is not unusual for them to live four to five years. A surprising fact about the brown recluse's biology is that these spiders can survive for long periods of time, up to six months, without food or water.

Female brown recluse spiders spin webs composed of irregular fibers that are loosely woven and very sticky. However, the web is not intended to catch prey, but rather serves more as a place of retreat for the spider. The brown recluse will roam at night in search of food, which is, preferably, live insects or other spiders, as long as they are small. If the spider chooses to dine on larger prey, it prefers that insect or spider to be dead. Also, the males will roam in search of females.