The duration baby spiders, known as spiderlings, stay with their mother varies significantly across species. Maternal care ranges from immediate independence to extended cohabitation, meaning there is no single answer.
Understanding Spiderling Development
Spiderlings are miniature versions of adult spiders when they first emerge from the egg sac. They are initially vulnerable due to their soft bodies. Spiderlings often sustain themselves on remnants of their yolk sac in the first days after hatching. To grow, spiders must shed their hard outer layer, an exoskeleton, through a process known as molting.
Molting allows the spiderling to expand in size. Young spiders molt frequently, often several times within their first year, and most species molt five to ten times before reaching adulthood. During molting, spiders are temporarily defenseless, as their new exoskeleton is soft and needs time to harden.
Variations in Maternal Care
Maternal care in spiders spans a wide spectrum. Many species, such as orb-weavers, exhibit minimal maternal involvement; mothers often abandon their egg sacs, and spiderlings disperse almost immediately after hatching.
Other species provide short-term care, guarding their offspring. Wolf spiders, for instance, carry their spherical egg sacs attached to their spinnerets until hatching. Once hatched, spiderlings instinctively climb onto the mother’s back, clinging to special knob-shaped hairs, and she carries them for several days to a few weeks until their first molt and dispersal. Nursery web spiders construct a silk “nursery web” to house and guard their egg sac. Spiderlings typically remain within this protective tent for about a week after hatching before venturing out independently.
Extended parental care is observed in a smaller number of species. Some social spiders, like Toxeus magnus, provide a milk-like fluid to their offspring for nearly 40 days, even past sexual maturity. Black lace-weaver spiders (Amaurobius ferox) lay unfertilized “trophic eggs” for their offspring to consume shortly after hatching, which boosts their weight and survival. In some instances, these spiderlings may even consume the mother (matriphagy) about one to two weeks after hatching, utilizing her body as a final food source. Some tarantula mothers guard their egg sacs and may protect their spiderlings, even sharing food in communal species.
Benefits of Maternal Association
Maternal association provides several advantages that increase the survival rate of spiderlings. Protection from predators and harsh environmental conditions is a primary benefit. The mother’s presence serves as a deterrent to potential threats, and she may actively defend her brood. For species like wolf spiders, the mother acts as a mobile refuge, carrying her young to safety.
Food acquisition is another significant benefit. Some spider mothers lay specialized trophic eggs, which are unfertilized eggs produced specifically for their offspring to eat, providing a nutritional boost. Additionally, certain species, such as the jumping spider Toxeus magnus, secrete a protein-rich, milk-like fluid to nourish their young. Mothers may also capture and share prey with their spiderlings, providing a consistent food source.
Spiderlings may also gain valuable insights by observing their mother. Young spiders can learn essential survival skills, such as hunting techniques and web-building, by observing their mother’s actions. The maternal web or burrow also offers a protected shelter, shielding spiderlings from adverse weather and providing a secure environment for development.
The Journey to Independence
After a period of maternal association, spiderlings embark on their journey to independence. The timing of this departure is often triggered by factors such as reaching a certain developmental stage, completing a molt, or diminishing food resources. Dispersal helps reduce competition for food among siblings and prevents cannibalism.
One common method of dispersal is ballooning, where spiderlings release fine silk threads into the air. These threads catch air currents, carrying the small spiders aloft and allowing them to travel varying distances, from a few meters to many kilometers. This airborne travel enables spiders to colonize new areas far from their birthplace.
Some spiderlings, particularly those from ground-dwelling species, disperse by simply walking or crawling away from the maternal site. Once dispersed, spiderlings are generally fully independent and self-sufficient, capable of finding their own food and shelter.