The anatomy of spiers is in some aspects similar, but also different from that of other arthropods. The following characteristics are common to all spiders: A body with two segments, eight legs, spinnerets, no chewing parts, no wings, and the presence of chelicerae, which spiders use to hold prey, and in most cases, inject venom. Spiders have non-compound eyes, with most species having eight; the spiders known as Haplogynae may have six or fewer, and certain cave-dwelling spiders may have none at all.