Crawling

Crawling is a form of locomotion characterized by close-to-ground movement in which the body is supported by limbs that pull or push against a surface. The term covers a range of mechanisms observed in humans, animals, robots, and software.

In humans, crawling typically begins in infancy as a developmental milestone. The classic crawl involves alternate movements of the arms and legs on hands and knees, producing a diagonal progression. Other forms include the commando crawl, where the body remains in contact with the ground as one crawls forward, and bear or crab crawls, which use different limb configurations. Crawling aids in mobility, balance, and sensory exploration, and is gradually replaced by walking as gross motor control develops.

In the animal kingdom, crawling describes a general mode of terrestrial locomotion used by many small mammals, reptiles, and invertebrates. It emphasizes a low posture and continuous contact with the substrate. Depending on the species, locomotion may rely on legged, pseudo-legs, or body undulations to propel forward.

In robotics, crawler designs imitate creeping motion to handle uneven terrain. Traditional track-based crawlers and inchworm-inspired systems use sequential bending and extension of body segments or articulated legs to achieve movement.

In computing, web crawling refers to automated retrieval of web pages by software agents known as crawlers or spiders. Crawlers index content for search engines, following hyperlinks and respecting robots.txt directives and rate limits to minimize server load and respect access policies.