Fishmail: Beetlemania

April 14th, 2006

Its time for some God stuff.

J.B.S. Haldane, one of the pioneering geneticists and most interesting scientists of the 20th century, was once asked what he had inferred about the Creator from his studies of the natural world. His exact response is hard to establish thanks to its many reported variants, but it was in a nutshell this:

If he exists, he has an inordinate fondness for beetles.

Haldane himself had an inordinate skill for being quotable perhaps more so than for being J.B.S. Haldane but his remark tells us something important about the world in which we live anyway. Leaving aside for one moment the trivial matter of whether God exists or not, it is worth considering for a moment just how important beetles are in the scheme of things. Some facts:

At least 350,000 species of beetle have been described, making them the largest group of creatures or plants on the planet. They account for about a fifth of all known living organisms, including plants and fungi, and about a quarter of all known animals. About half of them are weevils (and believe me, if I can squeeze a joke about the lesser of two weevils in here somewhere, I will). About 30,000 species are classified as scarab beetles, some of which are pretty impressive; the African goliath beetle can grow to six inches long and weight 4 ounces or so. Beetles live everywhere from salt lakes to savannas, rivers to rainforests, and there is nobody on the planet who does not come across them from time to time. Which raises an interesting question.

Why dont fish eat more of them?

Ive been thinking about this sort of thing recently as I wearily try to fill my fly box for the start of the new trout season. Bored to tears of tying damsel nymphs and buzzers and sedges, I figured Id try something new. Beetles sprang irresistibly to mind, not least because if there are so many of these rather fabulous creatures swanning around, youd expect that theyd be right up there on a trouts snack list; they are, after all, an exceptionally crunchy mouthful, truly the insect you can eat between meals without ruining your appetite. But then I started thinking harder about this, and it occurred to me that there are some very good reasons why I should stick to chironomids and odonates. The most important one is this: trout dont actually like beetles very much.

Now, I can just see the Sexyloops faithful all choking on their muesli at this point and screaming Hey! Ive got some beetle patterns! in my general direction. And yes, it is true that there are some flies out there which are given some sort of beetle appellation. Many patterns, such as the coch-y-bondhu, are widely held to be effective because of their beetle resemblances, but two interesting facts should help to exclude them from everyones fly box. The first is that not very many of these things actually look anything like beetles. They may well look like something else that trout like to eat, but not coleopterans. The second is that most fish really, really dont like eating them. We could, I suppose, argue about the first point with 350,00 comparisons to choose from, even a random selection from my flybox probably looks like a beetle of some kind - but the second is harder to dispute, once you look a bit more closely at what these remarkable creatures keep up their sleeves.

Nearly all beetles have a toxic armoury which would put Saddam's to shame. Even the humble ladybirds of which there are a mere 4,500 species worldwide secrete poisons with not just wonderful names (adaline, coccinelline, exochomine, hippodamine) but with seriously devastating effects on would-be predators. By the time we start looking at aquatic beetles which might be of interest to fly-fishers, such as the awesomely aggressive and predatory European diving beetle, Dytiscus marginalis, we discover that they secrete powerful steroids from their prothoracic and pygidial glands which can actually anaesthetise fish such as trout and pike and cause paralysis in carp. Force-feeding fish with water-beetle extracts results in an immediate rejection and flushing of the oral cavity the sort of response my flies normally get, of course and it seems fairly clear that these are creatures that are unlikely to be helping to fill a fish-basket anywhere near you in the foreseeable future.

Its not just fish who suffer from this, of course. Anyone who fancies a spot of beetle-sniffing as a cheap alternative to the pub on Saturday night can expect anything from ocular and respiratory irritation to impotence, dizziness, depression, weakness, fatigue, decrease in motor performance and even death; so dont try this at home, kids. Beetles are hardly unique in their ability to produce toxins, as anyone who has ever died as a result of eating a cyanogenic centipede will tell you, or not. But for insects that should on the face of things be perfectly good trout food, beetles are as good an example of how one can seriously waste ones time on the water or at the vice as I can think of. They are beautiful indeed to look at, fascinating in their behaviour and generally wonderful things to have around; just not on the end of your fly-line. I think Ill get back to my leech patterns instead.

Sean Geer ( is a freelance writer, journalist and fish pervert. He recently won the coveted Sexyloops Least Competent Fly-Tier award for the third year in a row, following a horrible accident with some deer hair and a bottle of red wine. In his spare time, Sean fails to write novels, makes barely credible origami fish and invents exciting new uses for tinsel.

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