Prosoma
Also called the cephalothorax. It carries the eyes, chelicerae, pedipalps, and four pairs of walking legs beneath a firm dorsal carapace.
Spider anatomy
Two body regions. An extraordinary machine.
Spiders are arachnids, not insects. Their compact design joins a sensory and mechanical front section to an abdomen that houses much of the animal’s internal machinery—including silk production.
Acanthoscurria geniculataEyes, pedipalps, and dense setae
Body map
Begin with the parts you can see.
The markers identify broad dorsal landmarks on a male Ceratogyrus darlingi. Fine structures and ventral organs are explained below rather than placed where this photograph cannot show them.
1234Abdomen
The opisthosoma is softer and usually unsegmented externally. It contains much of the digestive, reproductive, circulatory, respiratory, and silk-producing anatomy.
Eyes & mouthparts
Simple eyes sit near the front. Below them, chelicerae carry the fangs; pedipalps help with sensing, prey handling, and reproduction in mature males.
Eight walking legs
Each leg has seven main segments from coxa to tarsus. Muscles and internal fluid pressure work together to move different joints.
Verified close looks
Show only what the evidence can support.
Real photographs are used wherever the archive shows a structure clearly. The respiration card is an explicitly labelled conceptual diagram because the current photographs do not show the book-lung region well enough.
Eye cluster
Most spiders have eight simple eyes, though the number and arrangement vary. Several of Alma’s small reflective eyes are genuinely visible together above the mouthpart region.
Text only · exposed fangs not visible in the current archive
Chelicerae and fangs
The paired chelicerae are the first appendages. Each ends in a fang connected to a venom gland. They grasp and puncture prey; spiders take in liquefied food rather than chewing with jaws.
Text only · a true palpal-bulb macro is still needed
Pedipalps
The shorter appendage pair beside the chelicerae is richly sensory and helps handle prey. In adult males, the tips are modified into reproductive organs. A distant whole-animal photo was removed because it did not show those bulbs clearly enough.
Silk and webbing
Movable spinnerets sit at the rear of the abdomen. Different silk glands make materials for retreats, draglines, egg sacs, prey capture, and vibration-sensitive structures. This photograph shows the silk clearly, but not the spinnerets themselves.
Ventral anatomy and respiration
Mygalomorph spiders such as tarantulas usually have two pairs of book lungs. This simplified underside view marks the four external openings and the spinnerets; it does not claim to show the hidden, leaf-like lamellae inside.
Sensory hairs
Some setae detect touch and air movement. Slit-like strain sensors in the exoskeleton respond to mechanical forces, giving spiders a detailed sense of vibration. A photograph can show the hairs, but it cannot reveal each hair’s function by appearance alone.
Growth and molting
A rigid exoskeleton cannot expand continuously. A spider forms a new one beneath the old, lies on its back or side, withdraws from the old cuticle, and expands before the replacement hardens.
Read further
Anatomy sources.
This guide is a visual introduction, not a dissection manual. The references below provide more detail and diagrams.