The Myriapoda are a subphylum of Arthropods that comprises centipedes (Chilopoda: 1), millipedes (Diplopoda) and similarly structured sister Classes (Pauropoda: 12 & Symphyla: 11). Centipedes are mostly carnivorous and characterised by having venomous claws (4) as their first set of paired appendages. The metameric segmentation (repeated segments) of centipedes allows flexibility in the number of walking legs (one pair per segment) between species, however segments with walking legs always come in pairs hence the number of walking legs is only ever in multiples of four. The Symphyla are also known as pseudocentipedes and are much smaller, lack pigment and eyes, all of which suits their mostly subterrainean lifestyle living in pore spaces of soil eating decaying matter and root hairs. The Pauropoda are smaller still and, when seen, are found normally found in leaf litter. This chart illustrates the ganglia associated with each segment and its pair of walking legs (1: blue), male and female reproductive structures of the Chilopoda (6 & 7 respectively) and the initial development from an egg (8-10).
Anatomy of the orb-weaver spiders where structures of the open circulatory system are in red, alimentary canal in yellow, silk glands in light blue and poison glands in aqua green. The entire animal, longitudinal section is of a female (1) showing the ovary (Ov). The male testes (T) and vas deferens (V.df) are pictured dissected out (14). Note the pocketing of the alimentary canal creating the digestive diverticular (Cl1,2,3,4) viewed laterally (1) and dorsally (11). Other diagrams show various anterior appendages including pinching chelicera (2), pedipalps (3) and various fang shapes (8, 9 & 10). Other structures represented are the eyes (5), silk glands (6), book lung (12) and developmental stages (15 & 16).