Scotching myths about moths

13th July 2007 at 01:00
Moths are thought to have something of the night about them, but observing these prolific, colourful insects will reward pupils and teachers, says Ben Aldiss

Butterflies fluttering about the garden epitomise a summer's day, leaving us feeling that all's right with the world. Moths tend to evoke an entirely different response. We think of them as nasty, fluttery things that fly manically around our heads at night, or eat our clothes, or both. Butterfly Conservation, which campaigns to protect butterflies and moths, has just launched the National Moth Recording Scheme and wants to involve schools, so that the trend of venerating butterflies and denigrating moths can be changed for future generations.

The general ignorance about moths can be gauged from the reaction of my top set GCSE biology class, four of whom were chosen to attend the launch and meet Butterfly Conservation president Sir David Attenborough. "If there are 66 species of British butterfly, how many different kinds of moth do you think there are?" I asked.

Their answers ranged from 20 to 200, with most guessing around 30. There are about 900 larger moth species, but more than 2,500 altogether if you include the many "micros". Though most fly by night, there are spectacular and colourful species, and some which appear in daylight.

Moths are woefully under-represented in the curriculum, so getting involved in this campaign is an excellent opportunity to increase your pupils' knowledge of this vital link in the food chain. The future of many of our birds and mammals depends on them.


The largest British moths belong to the hawk moth family. The privet hawk moth is one of the most spectacular, and its caterpillars can be commonly found on privet hedges.

If your school has one, and you can persuade the groundsmen to leave 10 metres or so uncut until October, you may well find caterpillars. They are hard to miss 8cm long, green with purple stripes, and a black and yellow horn at the tail-end. This makes them attractive and instructive. Disruptive colouration, spiracles (openings to the gas-exchange system) and feeding mechanisms are easily studied without magnification.

The day-flying cinnabar moth has caterpillars that feed on ragwort, poisonous to horses, cattle and humans. The caterpillar and moth are immune, but use it by storing it in their tissues, so that predators avoid them. The caterpillar is warningly coloured, bright orange with horizontal black stripes.

Moths can be caught in moth traps fitted with lights and released unharmed the next day. This allows pupils to study their camouflage and sensory apparatus male emperor moth antennae are large and feathery and can detect a female 5km away. Also, a continuous record of species and numbers captured is useful and can be passed on to the county moth recorder for details of how to do this, see the Butterfly Conservation site.

You can buy easy-to-rear moth species, but keeping your own caterpillars on their foodplant is a cheaper alternative. Cut a pair of tights in two and cut off the feet, then stretch the tube over the branch your caterpillars are feeding on. Tie both ends and your captives are safe from predators, and can be collected for classroom use whenever required.

In my school we are going to set up our moth trap weekly throughout the academic year to try to identify and count each species we catch. The data can be plotted against a time axis, alongside climatic values, to see how different species appear at different times of the year and how their numbers might relate to weather conditions or food-plant availability. Such data handling and graph-plotting can be much more constructive than using data that bears no meaning to those who are expected to use it.

Whichever way you do it, following the life cycle using these methods is so much better than referring to boring diagrams in the textbook

Ben Aldiss teaches biology part-time at Thorpe House School in Norfolk. He also runs an A-level biology field course in the Pyrenees. He has set up the School Farm Wildlife Programme to cover the ecology element of A-level biology specifications, which can be contacted via:


Worldwide Butterflies (suppliers of stock to schools):

Butterfly Conservation (organisers of the Garden Moths Count): www.butterfly

Moths Count (information on moths and how to get involved on Garden Moths Count weekend): speciesmoths_recordingindex.php.


Learning to recognise different moth species develops powers of observation, so get pupils to construct their own identification keys and try them out on each other to enhance this skill.

Teaching pyramids of biomass - the amount of biological material at each level of a food chain - makes a lot more sense if you can demonstrate it practically. Keeping the huge, colourful caterpillars of the Indian moon moth in your science lab (see below for how to order) is not only fascinating, but easy and instructive.

By weighing the leaves provided as food, and the actual caterpillars, then weighing their droppings (these are dry, easily collected and relatively harmless just make sure hands are washed afterwards) you can calculate the relative masses of the first feeding position (trophic level) in the food chain (leaves) and the second (herbivores). Once the data from Butterfly Conservation's Moths Count weekend is available, schools will be able to compare the numbers of the 20 different species monitored and plot them in the form of a bar graph or pie chart. It may even be possible to compare catches from one area of the country with another.

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