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My research is a study of the ecology and diet preferences of the speckled bush cricket in two locations, one is coastal and one is in Oxfordshire. Previously I worked for the Medical Research Council where I was researching the medical effects of ionizing radiations and monitoring reports on radioactive discharges from nuclear power stations into marine environments.
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Dead wood? Not a bit of it - those logs offer rich habitats, explains Patricia Ash.
Have you ever rolled over a decaying log on a forest floor, and observed the teeming life found underneath?
Communities of invertebrates (animals without backbones) found amongst rotting logs play a crucial role in removing dead plant and animal material from the environment. Wood wasp and stag beetle larvae eat rotting wood, whereas beetle larvae, snails, slugs and millipedes eat soft decaying plant material.
There are fast-moving predators there too. Spiders prey on insects and woodlice. Common centipedes, brown in colour, and up to 3 cm long with 15 pairs of legs catch insects and slugs with their clawed front legs and inject lethal poison into them. Large black beetles such as devil’s coach horses and ground beetles emerge at night to catch slugs, spiders and insects with their sharp jaws.
If you have a log pile in your garden or have identified one in a wood or field, why not keep a record of the animals that are found there at various times of the year. Include vertebrates as well as the invertebrates to build up a picture of the food chains, and the diversity of life in your log pile. Good identification guides for insects, spiders, woodlice, snails and slugs can be bought from book shops or from the Field Studies Council. Bioimages offers an online guide to centipedes
The log pile environment
Small invertebrates, living under and amongst decaying logs are a community that is protected from dry air, insulated from extreme temperatures, and sheltered from predators such as birds. Exposure to below zero temperatures freezes and kills small animals like slugs, snails and woodlice. High temperatures kill small invertebrates as they reach lethal body temperatures surprisingly quickly.
The underside of a log provides a damp micro-environment. Slugs, snails, woodlice and worms do not have waterproofed skin and risk desiccation if they remain in a dry atmosphere for long.
Woodlice breathe by gills, which must be kept wet - drying out damages them. If their log is turned over, snails withdraw into their shells, slugs and millipedes crawl away, earthworms creep into their burrows, and centipedes, woodlice and earwigs scuttle off. What stimulates the animals into activity when their stones/logs are overturned? Are they reacting to light, because they prefer the dark? Or are they responding to the dryness of open air? You can investigate these questions by observing the responses of woodlice to light and humidity. First collect about 20 to 50 woodlice, preferably of the same species.
Identifying and observing woodpile dwellers: woodlice
Treat your woodlice gently and keep them in a clean margarine tub, with holes punched in the lid. Provide sliced vegetables or potato peelings that woodlice can hide in and eat. Woodlice are crustaceans, the group that contains lobsters and crabs, and we have 35 to 40 species of woodlice in the UK, and about 29 of these are native species. The Natural History Museum has a useful on-line woodlice identifier.
Place a woodlouse in a container and examine it with a magnifying glass or hand lens:
- What structures can you identify that could be the sense organs by which the animals detect cues in their environment such as light, humidity, food?
- Woodlice have a pair of antennae and a pair of eyes on the front of the head close to the bases of the antennae. Each eye consists of about 20 sub-units, resembling the compound eye of an insect
Investigation of choice of environment by woodlice
In their natural environment, woodlice do not have simple “choices”. A micro-environment may have favourable humidity but high temperature for example. To investigate choice of environment by woodlice try constructing a round choice chamber, (not square or rectangular, as corners provide extra unwanted micro-environments). Divide your box or tin into two compartments, which are connected to each other. Conditions that can be varied in each compartment include temperature, humidity, light, and food.
A key point is not to attempt to combine too many choices in one experiment. Begin by testing one option say, light, or humidity. Combinations of two choices can be tested once you have ascertained which ones the animals respond to.
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Content last updated: 17/10/2005
