Glow Worm - Lampyris noctiluca
 | About glow worms |
|---|---|
| Survey Form text file |
| Glow Worms by John Tyler - book details with photos. |
| Art work and photos |
| Foreign cousins |
Recommended reading:
This book is just about the only book on glow worms (click to see front cover). It is available for 5 pounds post free from John at Tadorna, Bradbourne Vale Road, Sevenoaks, Kent TN13 3DH.
Overseas customers should send either a cheque in pounds sterling for รบ6.50 or simply a US$10 bill which is just as acceptable. Please do not post cheques in foreign currency as they cost more to cash than they are worth. If you want to send notes in other currencies please ask before sending.
As we travel in our cars from one brightly streetlit area to another, we are unlikely to notice the tiny lights of glow-worms, about as bright as an LED indicator on a hi-fi. Yet they are still to be found, and they may be more common than you think. But despite surveys over the years, researchers are still in the dark over the factors affecting the decline of glow worms. What is needed is the widest possible survey of the remaining glow-worm habitats, which is where you can help.
The glow worm, Lampyris noctiluca, is not at all worm-like but is a beetle up to 25 mm long. Only the wingless female glows strongly, to attract the flying males. Each individual female has an adult glowing life of only a few weeks until she mates, since she dies soon after laying her eggs.
After a few weeks the eggs hatch into larvae, and they remain as larvae for one or two further summers, feeding on small snails which they apparently paralyse before sucking them empty. The two- or even three-year gap between a mating and the subsequent appearance of an adult helps to explain the characteristic 'boom or bust' cycles of glow-worm populations. It's possible to find plenty on a site one year, yet few or none at all the next. And, of course, sites where they seem to have died out can't be written off on the basis of a single night's search.
Where should you look for glow worms? Though they favour chalky or limestone areas, they have been reported in the past from many areas of Great Britain. People are often surprised to discover glow worms in gardens, hedgerows or railway embankments where they had never been noticed before. Disused railway lines are prime sites, in fact. Glow worms can also be found on cliffs, woodland rides, heathland and even valleys in Wales or Scotland which meet none of the above criteria!
Wherever you find small snails, though unfortunately not the large common-or-garden variety, it's worth looking for glow worms. They prefer open grass or hedges to woodland, but rarely are they to be found on land which has been 'improved' for agriculture. Look for them from late May to early September (with a peak in mid July), as soon as it gets dark. They glow for a few hours at a time, and usually stop glowing soon after mating. If you do see glow worms, don't disturb them and certainly don't take them home as trophies, no matter how many there are on a site. Their continued existence at your site could be on a knife-edge. But a short look by torchlight will do no harm, and you may see the smaller, darker (and glow-less) male mating -- perhaps even several on one female!
You may also spot larvae, particularly on dark, moonless nights. They glow much more faintly, and only intermittently, for a few seconds at a time. They are also not worm-like but have segmented bodies and six legs at the head end, quite similar to the adults. They do, however, sometimes help themselves along with their tails when moving, which makes them look a bit like caterpillars. You are more likely to see them on vegetation, searching for snails, than in the same areas as the glowing females. It is important for the survival of the glow worm to find the sites where the larvae live, since only about one per cent of its life is as an adult. Comparatively little is known about the preferred habitat of the larvae, so reports of them are always welcome. They appear over a longer time span than the adults, supposedly between April and October -- probably whenever conditions are right for snails and slugs.
Some people have asked about the conditions for encouraging glow worms or breeding them. We still do not know why some colonies die out even though there are no obvious factors such as destruction of habitat, use of pesticides or herbicides, or strong artificial lighting of the site. Glow worms need a supply of small snails as food (we are working on the preferred varieties) and therefore a patch of vegetation where they can find the snails. They also need a comparatively open area where the females can display to attract a male in June, July and August. As they retire into the ground during the day, mowing does not appear to affect them unduly and very long grass may actually not be very suitable. The females may appear on footpaths and there is therefore a danger period during summer if the path is heavily used in the late evening while they are emerging to glow. There is not much that can be done about this other than getting people to walk in single file.
As for breeding them, this has been done in the past with varying results. Even under favourable conditions there is a high mortality. Do not carry home glowing females hoping that they will lay eggs, or even catch a female that has apparently been mated in the hope of hatching a brood. It is better to leave them in the wild.
False trails
Virtually all the glow worms seen in Britain are Lampyris noctiluca. There is another species of glow worm in Britain, Phosphaenus hemipterus, which is vary rare and apparently seen only in parts of Sussex and Hampshire, though there are no recent records. The adult female is only 5-7 mm long compared with 12-20 mm for Lampyris (though bear in mind that the Lampyris larvae are often only a few millimetres long). Should you suspect that you have found Phosphaenus please contact either Robin Scagell (01895 637463) or John Tyler (01732 450775) immediately so that they can come and verify the identification. Please do not try and catch or kill Phosphaenus if you do see it.
There are other creatures that emit some luminescence, including caterpillars, and fungi can also glow. Another cause of false reports of glow worms is actually light reflected from shiny leaves, dew or litter. It is therefore vital to check that what you see really is a beetle with the light coming from the final tail segments.
Finally, we get occasional reports of fireflies in Britain. The authorities say that they do not exist here, and it is probable that the reports refer to other flying insects seen in light beams. True fireflies swarm around a clump of bushes or in a glade and are visible over a greater distance than glow worms. If you do come across fireflies in Britain then make every effort to catch and keep one (dead or alive!) and let us know immediately.
This may look detailed, but if parts of it do not apply to your site or are hard to fill in just leave them blank. Some people are worried that if they give details of a site people may come and collect the glow worms, but the information on the forms will not be sent out to others. It is better that we know exactly where glow worms are to be found so that changes can be monitored over the years. We would welcome reports in future years as well, so please don't stop looking for glow worms after this summer.
International reports
We have few contacts with glow-worm researchers in other countries. Though our survey is really intended only for the UK, and we are not set up for maintaining a database in other countries, we are happy to receive reports from other countries and will keep them on file. We do receive requests from other countries for information and it may come in useful in the future. We have not heard of any other European surveys of either glow worms or fireflies, though there is a firefly newsletter in the US, available at cost from Prof. J E Lloyd, Dept of Entomology, Bldg 970, Hull Road, Univ of Florida, Gainesville FL 32611.
Robin Scagell: 100014.2426@compuserve.com
Links to web sites on foreign glow worm and firefly species
... on it's way !
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