Small is beautiful: Let’s hear it for insects
They pollinate our crops and break down waste but we have very little data on them
In Ireland, the best we have are six years of data on a small number bumblebee species, and 10 years’ worth on a small number butterfly species.
At last, we’re on the right side of the spring solstice. To me, longer days mean fewer excuses for standing (or, if I’m honest, sitting) idly by while my garden grows itself into chaos. Gardens are strange things: the intentional communities of the plant world, brought together by the will of the gardener on the basis of their appeal to the senses, and then fed, pruned and coerced into thriving.
They are to the notion of wildness what a labradoodle is to a wolf. But just as animal lovers often trace their passions back to childhood experiences with beloved pets, the passions of many nature lovers were sown in the most unnatural of gardens.
And yet, despite their regular appearances in said gardens, it’s comparatively rare that people’s passions extend to insects. It’s easy to speculate on the reasons for this. Insects are annoying. They bite. They get in your drinks in summer. They eat holes in your jumpers in winter. They terrorise the ketchup at barbeques. They fester in your kitchen compost bin and seem to reproduce in powers of 10 per second.
Even the word is ugly. No part of it evokes the splendour of a brightly pigmented butterfly, or the iridescent rainbows on the underside of a beetle, or the romance of a mayfly’s brief above-water lifecycle, or the charming fuzziness of a bumblebee. Maybe that’s why, when we hear about the decimation of insect populations at a global scale, we have to remind ourselves why we’re bothered.
Of course, we should be. Insects pollinate our crops and wildflowers. They help to break down wastes. They comprise a significant proportion of the food chain’s lower links. And, as my entomologist colleagues would be keen to point out, they are utterly fascinating in their diversity, complexity and downright weirdness, and worthy of our interest irrespective of their contribution to human wellbeing.
To illustrate this, they might refer to the planet’s estimated 5.5 million-odd species of insect and compare it to the meagre 5,000 species of mammal, and point out the thumb-sized bee (Megachile pluto), or the one (Perdita minima) that’s so small it can sit on the head of a pin. They might talk about honeypot ants, who milk aphids for their sugary poo, drink it and regurgitate it into the mouths of other ants who hang from the ceiling and store it for later like tiny insect vending machines.
They might also vent their frustration at aforementioned headlines about global decimation of insect populations. Not at the fact of the headlines, but rather at the scantiness of the detail underlying them. Truth is, we have perilously little data on insects in Ireland.
To make rigorous estimates of declines, we need long-term ecological studies over decades. But there are none in Ireland. The best we have are six years of data on a small number bumblebee species, and 10 years’ worth on a small number butterfly species. These are minuscule datasets that make comparisons statistically dodgy.
While we can look at global trends and confidently deduce that yes, we have a problem, and no, it’s not just us, the sparseness of our own data makes figuring out what to do about it especially tricky. Bumblebees and butterflies are good indicators for other types of insect, but they are terrestrial vegetarians. What they need is very different to what aquatic insects need (and they’re in even bigger trouble than the landlubbers), and different again to the needs of meat-eating insects, or parasitoids, or insects that feed on wastes.
They’re also unfussy generalists, and while the interventions that work for them are likely to be at least somewhat beneficial for most other insects, they don’t tell us anything about how to protect specialists who have such refined tastes that their entire existence might depend on a single type of flower.
This is the case with the pearl-bordered fritillary butterfly, whose larvae will only eat common dog violets, which only grow on sheltered, dry, un-enriched grasslands, which only occur with a particular level of scrub removal in the Burren and Lower Lough Corrib. Compare this to the far less picky small copper, which is satisfied with a simple diet of docks and sorrel, and yet is also declining.
The only things sparser than Ireland’s insect data are the volunteers that we rely on to collect it. Eighty people are responsible for everything we know about bumblebee populations and 115 people (some of whom are also in the former group) are responsible for everything we know about butterfly populations. Compare those numbers to the 11,000 species of insect that we have in Ireland and you’ll grasp the scale of the challenge. Something to ponder when you’re weeding the garden this spring...