Where do all the insects go in winter?
Where do all the insects go in winter? I hear you never ask.
Which is just as well because I don’t have the answer! This is something that I’ve been thinking about more and more though, and as I watch the countryside, I hope that some of the secrets begin to unveil themselves so that I can manage my own garden in a way that’s as nature friendly as possible.
To answer this we need to know a little about insect life cycles. I don’t suppose that we’ve got time here to look at all 20,000 of our British insect species and the answer of course is, it depends on which insect.
Insects, being cold blooded, can't usually survive a British winter being exposed to the elements so employ various strategies to overwinter. If we were to look only at butterflies we’d start to get an idea of the picture.
There are only 59 resident or regular migrant butterflies to Britain and they go through 4 stages of life cycle - ovum (egg), larvae (caterpillar), pupa (christalis) and imago (butterfly).
The vast majority of plant eating insects are what’s called specialist feeders, this means that they have evolved alongside either one or very few specific plants and built up resistance to their defensive chemicals designed to be unpalatable to other insects. Adults are more often generalist feeders able to use the nectar of various plants which is basically sugary water. Butterflies are no different and eggs will be laid on or nearby the food plant of the caterpillar with the larvae going through several stages called instars, moulting its skin and emerging as a slightly, or towards the later instars, quite radically different looking caterpillar.
To make the original question slightly more tricky, Butterfly Conservation tell us that British butterflies, depending on the species, can overwinter as any one of their life cycle stages with 9 overwintering as eggs, 31 spending it as caterpillars, 11 as a chrysalis and the remaining as adults.
Caterpillars can wrap themselves with silk in grass sheaths, or leaves, bury themselves underground, or slow down their munching at the base of grass tussocks. A chrysalis might hang from a low branch or be buried in leaves and adults find shelter or leave the country.
Probably the four butterflies that I notice most are the meadow brown (Maniola jurtina) peacock (Aglais io), red admiral (Vanessa atalanta) and comma (Polygonia c-album).
Two of these species, the peacock and comma butterflies go into a state similar to hibernation as adults in sites such as on sheltered tree trunks, in hollow trees, woodpiles or the crevices of buildings. Probably our most common butterfly, the meadow brown overwinters as a caterpillar at the base of grasses and the red admiral generally and sensibly in my opinion, overwinters in the warmer climes of southern Europe and North Africa.
The peacock, red admiral and comma butterflies, by the way, all share hop (Humulus lupulus) or common nettle (Urtica dioica) as their sole food source. With the larvae food plant of the meadow brown as mentioned above being native grasses.
So how does this help me manage my garden? I guess it’s a balance, as least disturbance as possible protects overwintering insects, but a meadow for example, to invigorate the growth of plants pollinated by insects (nectar providing plants), disturbance, light and reduction of competition by the cutting of grasses is required. My personal preference is to leave mostly alone and seed native wild flowers outside of the majority of the grassland. Tidy to a level that is minimal but tolerable, and allow areas of untouched scrub, but each of us have our limits and if anyone comes to my garden they’ll know my limits are loose bordering on feral, much like myself.
