Oniscus asellus
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| Oniscus asellus Linnaeus, 1758 |
Oniscus asellus, the common woodlouse, is one of the largest and commonest species of woodlouse in the British Isles and Western Europe, growing to lengths of 16 mm and and widths of 6 mm. They are generally flatter than other large woodlice, and their bodies are usually brownish-black in colour, with paler mottling and very pale edges to their segmental plates. Their carapace is usually rather shiny, while the underside is pale. The species can also be identified by its long pointed telson. Oniscus asellus has a strong exoskeleton and seven pairs of legs, but are born with six pairs. They have antennae that reach about half of their body length, which they use to feel around in their dark environment. Other common names include the common shiny woodlouse and more colloquially tiggyhogs, God's little pigs, "parsons-pigs", "grammer sows" and sowbugs.
[edit] Ecology
The species is particularly fond of rotting wood and are one of the commonest species found under garden logs and stones in their range. They are also likely to be found in houses which have damp porches, in outhouses, back kitchens and so on.
These woodlouse eat vegetables, various types of detritus such as dead plant and animal matter, including rotting wood. They are very effective decomposers; this means they are often an integral part of a compost heap.
Oniscus asellus predators include toads; shrews, hedgehogs, young owls and foxes, centipedes and spiders such as the woodlouse spider(such as Dysdera crocata), which has evolved fangs which are well-suited for piercing the woodlouse's exoskeleton and injecting poisons.
[edit] Behaviour
Oniscus asellus has reflexes such as running away or rolling into a ball upon seeing a predator. Upon meeting, these woodlouse tap each others antenna as if swapping messages. After a moult, the woodlouse may eat its own exuvia to reabsorb the calcium carbonate. Oniscus asellus can reproduce both sexually and asexually. In sexual reproduction, which usually occurs in the dark, the male courts the female by waving his antennae at her. During reproduction the male climbs onto the female's back. He licks her head and taps her back with his front set of legs. The male will then move into a diagonal position to one side, he then bends his body under her so his genitalia reach her genital opening on the opposite side. Sperm is transferred within 5 minutes, the process is then reversed and the male approaches from the other side.
