The daddy of all bugs

Noticed all the crane flies in your kitchen? The warm, wet autumn means Daddy-Longlegs has never had it so good. Peter Forbes tracks the march of an endearingly silly insect
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Climate change is causing a boom in the numbers of many creatures, some dangerous, some a nuisance and some, perhaps, a bonus. The plague of locusts that raged through Africa and southern Europe over the past year was truly terrifying, consuming all vegetation, wild and agricultural, in its path.

We don't have locusts in Britain - yet - but we do have the dear old daddy-longlegs. I say "dear old" because I've always regarded them as amiable harbingers of autumn. These things are very subjective: for some, the name is confused with the daddy-longlegs spider; for others, it evokes no more than the title of an unthreatening Fred Astaire film.

Daddy-longlegs fly into the house on balmy evenings at this time of year and stagger around the room. If left alone, they are found a few days later dead in a corner somewhere.

It's a good year for daddy-long-legs, at least in some parts of the country. London is quiet, but blogs from the Midlands and North report unusual numbers. There are fears of an epidemic in some parts of Northern Ireland. Should we be worried?

Stuart Hine, the manager of Insect Information Services at the Natural History Museum, welcomes the phenomenon cautiously. "It's not an unprecedented crop," he says. "It's about the normal maximum, and I don't expect to see increasing plagues of them in the next few years. One reason we're noticing them so much now is that it's warm for the time of year. Doors and windows are open, so they fly in."

Which is when, for some people, the trouble starts. Daddy-longlegs (or crane flies, to give them their formal name) are insects, not spiders, but for people who suffer from arachnophobia they trigger a similar response. An arachnophobe of my acquaintance says: "The reason they don't scare me as much as spiders is that they're so ethereal. They don't have the gross, hairy quality of spiders. But what disturbs me is their ability to flutter all over me without any control and to shed their legs."

They do seem rather gormless once inside the house. Hine says they're good fliers outside, but in the presence of bright lights they become confused. "They make a fool of you, running round the room trying to catch them, but they're completely harmless. They're food for many other creatures."

For Hine, public interest in any insect species is good because it raises awareness. "When you're fed up with chasing daddy-longlegs, look around and see what else you can see."

Daddy-longlegs don't bite; indeed, they hardly eat at all. As adults, their purpose is to mate and to die within a few days. Mostly they have enough food stored up within them to do this, although they might sip a little nectar to get themselves in the mood.

Daddy-longlegs are only a nuisance in one phase of their life cycle. Their larvae are leatherjackets, those reddish-brown nuggetty things you find in the soil. They live on the roots of grass and cereals, and can be a pest. There might be half a million or more in a single hectare of soil. Birds, especially starlings, keep them under control.

It isn't only crops that are at risk from leatherjackets. The last two flat meetings at Chepstow racecourse were cancelled because of infestation of the turf, but the first meeting of the jumps season will go ahead on 8 October after remedial action.

To us, the life cycle of the daddy-longlegs, like all larval insects, seems weirdly unbalanced. The creatures you see now are mating. The eggs they lay will hatch into larvae in two weeks' time. The leatherjackets will live through the winter, spring and summer, for up to 10 months. They like damp conditions, and this year's rain has been nicely spaced to keep them happy. The adults - which to us seem the point of the whole exercise - live for only a few days.

As the name suggests, crane flies are mechanical-looking creatures. In Fleur Adock's poem "Coupling", their mating is likened to jump-starting a car: "The larger cranefly is jump starting the smaller cranefly... their engines seem to be in the rear". The poem concludes that their mating is so neat, it ought to be an inspiration to us all.

The Insect Play by the Capek brothers gives the creatures a voice. Through most of Act II, a larva is ecstatically waiting to be born: "O universe, prepare! O space, expand! The mightiest of all happenings is at hand." The larva is consumed before the wondrous act can take place but, even if it had survived, the brevity of its airborne life would have made a mockery of the long months of preparation.

Not content with increasing their presence in British houses, European crane flies have recently acquired global ambitions. In the last two years, they have appeared in numbers in the eastern United States and their larvae are causing problems with crops. In cereal fields, once the crops have reached a certain height, birds cannot get at the leatherjackets and the roots of the crop are damaged.

An adult crane fly can dispense with several of its legs and up to 80 per cent of its wing area and still achieve its goal of mating. The very flimsiness of the insect is actually part of its survival strategy.

It is a creature not to be despised - and certainly not one to be feared.

No, they're not spiders

At least 14,000 species of daddy-longlegs, or crane flies, have been described, most of them by the entomologist Charles P Alexander, who died in 1981 at the age of 92.

The giant crane fly of the western United States can reach 38mm in length, although some species can reach 64mm. There are many smaller species, known as bobbing gnats, that are mosquito-sized, but they can be distinguished by a V-shaped suture on the thorax and their lack of ocelli, or photoreceptor organs.

* Daddy-longlegs do not bite humans. They drink only water when young and do not usually feed at all when they are adult, as they only live for a few days to mate.

The animal that many biologists call "daddy-longlegs" is a spider, Pholcus phalangioides, which belongs to the spider family Pholcidae, order Araneida, class Arachnida. Pholcid spiders kill and digest their prey using venom. However, there is no scientific basis for the urban myth that daddy-longlegs spiders are the most venomous, poisonous or toxic spiders in the world. Daddy-longlegs spiders do have venom glands and fangs, but their tiny fangs are fused at the base and they cannot open their jaws wide enough to bite humans. In addition, there is no evidence in scientific literature to suggest that the venom of daddy-longlegs spiders is potent enough to harm humans.

Peter Forbes's 'The Gecko's Foot: Bio-Inspiration - engineering new materials and devices from nature' is published by Fourth Estate