CATERPILLARS AND THE
LEAVES THEY LOVE TO EAT

Our Butterflies in Decline
Many of us will have noticed a fall in butterfly numbers over the last few decades. No, it's not our imagination; detailed surveys support our suspicions. Butterflies and other invertebrates are being wiped out as their habitats are destroyed, and the specific wildflowers on which they feed and seek shelter are lost.

Butterflies and other invertebrates bring the countryside, a park or garden to life; it is not the same without them.

Why so Steep a Decline?
Figures showing a fall of fifty or eighty percent in the number of different kinds of butterfly over the last few decades are so typical we almost tend to be grateful when it is at the lower end of the range. The situation in Britain is similar to that in most countries in that the main causes of habitat destruction and the consequent loss of wildlife are the relentless intensification of agriculture and urbanisation.

Insecticides
Crop protection involves the direct killing of insects by insecticides, much of it indiscriminate, regardless of whether they are actually the species causing the damage, or predators of them.

Herbicides
But far more harmful overall is the effect of herbicides targeted at the native vegetation on which butterflies and their caterpillars, and countless other invertebrates, feed. Herbicides, along with soil preparation techniques, uprooting and destruction of hedgerows, draining of marsh land, and the  development of aggressive crops which choke out everything else in their path, result in widespread starvation in the insect world and among the birds and mammals that feed on them. A typical field is now a wildlife desert.

Increased urbanisation
There are of course other causes of declining biodiversity. Road building is one. The duelling of the A90 in Scotland for instance is causing habitat destruction on a massive scale, while increased urbanisation produces housing estates with virtual gardens where soil is replaced by block paving, and flowers by a bunch of brightly coloured cars.

OUR AIM
Our aim at CATERPILLAR FOOD PLANTS is to  suggest ways in which we can slow down the rate of destruction and bring back the butterflies by growing more of the native wildflowers and leafy vegetation essential for their survival. Adult butterflies drink nectar and/or other sugary drinks, but their caterpillars need their greens. And when they are in short supply, we need to provide them.

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Wildflower Meadows providing
Nectar and Pollen for Bees and Adult Butterflies
There has been a lot of interest in recent years in the sowing of wildflower meadows, and wildflowers in general, to help meet the nectar requirements of adult butterflies and the dual nectar and pollen requirements of bees.

This is excellent, but It's worth remembering that of the thousands of species of insect native to Britain, not all actually drink nectar or eat pollen, just the high profile pollinators - butterflies, moths and bees, hoverflies and a few others, and then with very few exceptions, like bees, only as adults.

Bees are extremely unusual insects in that they feed both on nectar and on pollen, and that they do so both as adults and as larvae.  Butterflies and moths in contrast - with a few tropical exceptions - do not consume pollen at all, and some do not even drink nectar, preferring to refuel on aphid honeydew or rotting fruit. Those butterflies that do drink nectar, do so only as adults. Many insects feed on neither pollen nor nectar at any stage of their lives.

Beyond the Nectar - Caterpillars Need their Greens
We encourage visitors to our website to look beyond the nectar and to appreciate the needs of butterflies and moths at all stages of their lives. This begins with the laying of eggs by the females after a careful search to find just the right plant and location, taking into account the needs of her caterpillars for nutrition, warmth, camouflage, and defense.

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 We therefore emphasise the importance of providing not only adult butterflies with nectar but their much more selective caterpillars with the special diet that they need.

Adult butterflies don't particularly care what flowers they get their nectar from, but they do care what kind of leaves or buds they lay their eggs on. This is because their caterpillars can only eat  the leaves of a very small number of different kinds of plant, in some cases they are limited to just one species.

There are various reasons for this:

• Most plants produce insecticides to protect themselves against insects, and most species of insect have evolved to protect themselves against just a few of these toxins.
• Secondly caterpillars have evolved camouflage to blend in with the colour and shape of the leaves (or buds) they feed on.  If the female butterfly lays her eggs on the wrong kind of leaf, her young will be much more visible to predators.
•  Thirdly, many species have evolved methods of concentrating distasteful substances from the leaves to make themselves unpalatable to birds.

These caterpillar foodplants are not necessarily present in the popular commercial wildflower mixes that supply the flowers for pollinators simply because a lot of such foodplants are wind pollinated and so don't produce meadow-ready pretty flowers, and there are others that for one reason or another rarely appear in wildflower nectar mixes.

The good news, however, is that it would be difficult to find a component of a wildflower mix that wasn't a larval food plant for one insect or another. Each is virtually guaranteed to boost biodiversity beyond its own presence.

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There will also be a need, to be discussed later, for suitable pupation and hibernation sites in crevices in trees and among clumps of vegetation.

A Bio-diverse Green Garden or Block Paving; Which Would You Choose?

A network of bio-diverse gardens is often promoted.as a way of mitigating the excesses of agriculture. There are millions of gardens in the UK and if they were all rich with wild flowers they could be havens of wildlife, home to invertebrate, birds, mammals and amphibians.

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Unfortunately the trend on the ground continues to be very much in the opposite direction with more and more householders abandoning their front gardens in favour of dark, soulless expanses of gravel and block paving, with not a flower, even an exotic one, in sight.

Butterflies are often regarded as an indicator of the health or otherwise of the countryside - what happens to them is likely to be happening to thousands of other equally important but perhaps less flamboyant and colourful insects. Whatever small steps we take to help bring back the butterflies, even if the butterflies themselves fail to respond, is therefore likely to be of benefit to many other invertebrates.

Our aim is to increase awareness of the wildflower foodplants essential to the survival of butterfly caterpillars, and to help in selecting those most suitable for the butterflies likely to be present in your part of Britain and Ireland.

Text copyright Trevor Smith April 2019

The images that are not my own are from photographers who generously make their photographs available via Pixabay.com.

For more information about the butterflies mentioned in this website and others we recommend Butterflies of Britain and Ireland by Jeremy Thomas and Richard Lewington, 2019, ISBN 9781472967190.

The following websites also contain lots of useful information.
www.ukbutterflies.co.uk
www.butterfly-conservation.org

Beyond the Nectar
to the Needs of the Caterpillar