Dear Readers, you can tell it’s autumn when these flies start to emerge from the lawns where they’ve been living as leatherjackets and no doubt causing all sorts of damage to the grass roots. In Somerset and Dorset you can see them silhouetted against the painted walls of houses or the gleaming white surfaces of garage doors. They are so clumsy in flight that you’d think they’d all be picked off by predators immediately, which is probably why they emerge en masse, in the hope that at least some of them will survive. Once landed, however, they always seem to have a kind of posed elegance about them.
In the UK we think of these insects as ‘daddy longlegs’, but in some parts of the country we also use this name to describe harvestmen, and I believe that in North America it means a cellar spider. Thank goodness for scientific binomial names, so we all know what we’re talking about.
Crane flies evolved very early in the history of the fly family (Diptera),and there are over 15,000 species worldwide, with some reaching a wingspan of over 4 inches, although the larger species tend to be tropical. I always think that their heads look a little like horses. Horses from hell possibly, but horses nonetheless.
The mass emergence is also explained by the life cycle of the crane fly. When a female emerges from her pupa, she already has mature eggs inside her, just waiting for fertilization. The males immediately begin to search for a partner – the fly in my photo is a female, with a swollen abdomen. She seemed to me to be looking for somewhere to lay her eggs, though a garage door is probably not an ideal spot – usually the eggs are laid in damp soil. Adult flies live for 12 to 15 days and in this species don’t feed during this time. I have read articles indicating that crane flies eat mosquitoes, but this is clearly impossible.
Once laid, the eggs turn into grubs known as leatherjackets in the UK. They are food for many animals, including moles, shrews, birds of various species and many other insects, but they can also cause havoc on a lawn. It was reported that there was an infestation of leatherjackets at Lords Cricket Ground in 1935, as reported by A. Ward in ‘Cricket’s Strangest Matches’ (1999).
‘Several thousand were collected by ground staff and burned, because they caused bald patches on the pitch and the pitch took unaccustomed spin for much of the season.’
As a child I was horrified by crane flies – I mistook their inept flying as a determined attempt to chase me around the living room. The insects seem to have a zombie-like ability to survive even the most enthusiastic swat, and I remember sitting in the living room, relieved that a crane fly had been dispatched, only to hear a strange rustling in the waste paper bin. After a few seconds a battered crane fly rose as if from the dead and started flying in my general direction, until my grandmother delivered it the final blow. Nowadays I realise that crane flies are not only completely harmless but an important part of the ecosystem, providing many migrating birds with a leggy but nutritious beakful on their way south, and providing late dragonflies with a feast. The leatherjackets of many species help to clean up the soil by eating detritus and decaying matter too. Plus, there just aren’t as many crane flies, or insects in general, about these days, poor things. Seeing half a dozen in Somerset, in Hilary’s garden, was a reminder of how rich in invertebrates our country used to be, and how impoverished it is now.
And so to a final myth about crane flies. Every year, someone announces that they are the most venomous animals in the world, although they have no means of administering the poison. This is completely untrue. Poison production is extremely expensive for the animal involved, so it would be unlikely to have evolved in an animal with such a short life as an adult. Plus, the majority of craneflies are not predators, so what would the poison be for? I wonder if this idea emerged because of confusion with the cellar spider which, like all spiders, does have venom, but is totally harmless to humans.
So, this year I was happy to watch the crane flies flying sideways, landing with a bang in the long grass and posing on the garage door. I was amused to see a tiny jumping spider about a tenth of the size of the crane fly eyeing it up as dinner with what passes for a confused expression if you’re a spider. I had never thought of these creatures as beautiful, but I did love the elegance of those long-legs mirrored by their shadow. I hope that this one enjoyed her short life in the late, long sunshine of the end of September.