Tarantulas are a group of spiders recognized for their substantial size and often hairy appearance. They exhibit diversity in size, color, and structural features.
Overall Impression and Size
Tarantulas generally present a robust and somewhat heavy-bodied appearance, distinguishing them from many other spider families. Their entire body, including their legs, is typically covered in a dense layer of hairs, contributing to their characteristic furry texture. This hairiness gives them a soft, almost plush visual quality.
The actual size of a tarantula can vary significantly across the numerous species. Some of the smallest species, often referred to as dwarf tarantulas, like those in the Cyriocosmus genus, might have a leg span of only 2 to 3 inches (5 to 7.6 cm). In contrast, the largest species, such as the Goliath Birdeater (Theraphosa blondi), can boast an impressive leg span exceeding 10 to 12 inches (25 to 30 cm), making them among the largest spiders in the world. This wide range means that while all tarantulas share a general body plan, their overall dimensions can differ dramatically depending on the specific species.
Main Body Structure
A tarantula’s body is distinctly divided into two primary segments: the cephalothorax and the abdomen. The cephalothorax, also known as the prosoma, is the fused head and thorax region. It is covered by a hard, shield-like exoskeleton called the carapace, which provides protection for the vital organs beneath.
A small, central indentation called the fovea is often visible on the dorsal surface of the carapace. All eight legs, the pedipalps, and the fangs are visibly attached to this cephalothorax segment. Behind the cephalothorax lies the abdomen, or opisthosoma, which appears softer and more rounded in comparison. This posterior segment is typically covered in fine hairs and houses the spinnerets at its rear, which are small, finger-like appendages used for producing silk.
Legs, Pedipalps, and Fangs
Tarantulas possess eight prominent legs, all originating from the cephalothorax. Each leg is segmented, allowing for a wide range of movement, and is typically covered in the same dense, often bristly hairs found on the rest of the body. At the very tips of their legs, tarantulas have small claws, which assist in gripping various surfaces.
Additionally, many species feature specialized pads of dense hair called scopulae on their tarsi, the very last segment of their legs, providing excellent traction for climbing and adhering to smooth surfaces. Located near the mouth, tarantulas also have a pair of pedipalps, which resemble a shorter, fifth pair of legs. These appendages are primarily sensory, used for feeling and manipulating objects, and are also covered in hairs. Below the mouth are the chelicerae, which are stout structures that house the fangs, appearing as two downward-pointing projections.
Coloration and Distinctive Features
Tarantulas exhibit an incredibly diverse palette of colors and patterns across their many species. While many are shades of brown, black, or grey, some species display vibrant hues of blue, green, red, orange, and even purple. For instance, the Cobalt Blue tarantula (Haplopelma lividum) is known for its striking iridescent blue legs. This iridescence creates a shimmering effect, where colors appear to shift and change depending on the angle of light.
Many species also possess urticating hairs, which are specialized barbed bristles primarily located on the dorsal surface of their abdomen. Sexual dimorphism, differences in appearance between males and females, is common. Males are often more slender with longer legs relative to their body size and may develop tibial spurs, hook-like projections on their front legs used during mating. Molting, where a tarantula sheds its old exoskeleton, often results in a fresh, more vibrant coloration as the new exoskeleton hardens.