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SUBPHYLUM MYRIAPODA

This Subphylum contains four classes, Chilopoda, Symphyla, Diplopoda and Pauropoda. All follow the body plan of head and trunk.

Class Diplopoda These are the millipedes, there are over 10 000 species, and all are terrestrial. They can reach 28 cm in length, and have fairly cylindrical bodies of between 25 and 100 segments. The body of millipedes is often specialised to enable the animal to roll into a ball (see the pill millipede below) or coil (see the tropical millipede on the left. Unlike the Chilopods (centipedes), each segment has two pairs of legs and two pairs of spiracles. No millipede has a thousand legs, the largest, from West Africa, barely reach 400. However a tiny millipede, Illacme plenipes, found in one single ravine in San Benito, California, and thought to have gone extinct until recently has up to 750 legs in the female. She is only 3.2 cm long and 0.05 cm wide. The male has between 300 - 400 legs. Millipede larvae have only one pair of legs to each segment, and fewer segments than the adult form, see below.

Above is a tropical millipede. Millipedes have two groups of simple eyes. Their sexual organs are on the second segment behind the head, and the female lays eggs in a nest. They are mainly herbivorous or detrivorous, and can escape predation by rolling up or secreting toxic fluids from repugnatorial glands. They tend to prefer dark, moist habitats.

The large tropical millipedes make popular and easy to care for pets, and surely few things on this planet are as elegant as the red-legged millipede out for a stroll.

On the left is Glomeris marginata, the pill millipede. It is often mistaken for a woodlouse, but it has more legs (10 or more pairs) and a shinier body. When disturbed it can roll itself into a ball - hence its common name. It tends to be found in calcareous, grassy soils. When fully grown it can be up to 2 cm long.

Below is Pauropus silvaticus.

Class Symphyla

These are small, from 2 mm - 10 mm. They resemble centipedes, and there are around 160 species world wide. They are found in moist habitats such as leaf mould. Most can run fast. They feed on vegatation. Scutigerella immaculata (left) can be a pest in greenhouses.

Mating is unusual in the Scutigerella. The male depositis his spermatophore at the end of a stalk. When the female finds it she eats it, but she does not swallow the sperm. She stores it in special pouches in her mouth. When she is ready to lay an egg she removes it as it emerges using her mouth, and attaches it to the soil or leaf mould. In doing this each egg gets smeared with sperm. There are usually around 35 eggs and they are attached to the leaf mould, moss or lichen. Parthenogenisis is also common. On hatching the young have only 6 or 7 pairs of legs. The number increases with each moult. They moult even in adulthood.

Scutigerella immaculata can live for as long as 4 years.

Class Pauropoda

All in this class are less than 2 mm long, and have soft bodies. There are around 500 species world wide. They have branched antennae (see right) and no eyes. Usually they have nine pairs of legs. It is believed that they are related to the millipedes, but more primitive. They inhabit moist environments such as leaf litter, under bark and in decaying vegetation and debris. They are usually a pale, whitish colour.