Last summer I developed a bit of an obsession with the ladybird lifecycle. I collected the pupae of harlequin ladybirds, put each one in a jam jar and waited to see what emerged...
Last summer I developed a bit of an obsession with the ladybird lifecycle. I collected the pupae of harlequin ladybirds, put each one in a jam jar and waited to see what emerged from them. Not surprisingly, every one of them yielded a harlequin ladybird, which was safely deposited outside, none the worse for its short spell living in a jam jar in the Gardeners’ World Magazine office.
I was prompted to do this for the Ladybird Parasite Survey. The survey aims to find out how much harlequin ladybirds are being parasitised and whether, in time, these parasites will help stymie the spread of the harlequin across the UK. It also tracks the speed with which nature is adapting to the presence of this foreign invader; evolution in action.
I’m very up-to-date with the harlequin invasion at the moment, having written about it in the April issue of Gardeners’ World Magazine and discussed it with Helen Roy of the UK Ladybird Survey on Gardeners’ Question Time. Recent research has proved that harlequins are responsible for the 44 per cent decline in the 2-spot ladybird, and are also threatening other native species. On top of that, harlequins have been found to eat lacewing, moth and butterfly eggs, so could potentially trigger the decline of many insect species and their predators (other insects, birds and bats).
All ladybirds start their lives as eggs. They hatch into larvae, which usually spend a couple of weeks eating aphids before pupating into a dome-like structure, metamorphosing into an adult and finally emerging like a butterfly from a chrysalis. Ladybird parasites (or parasitoids, to be precise) are nothing new, and provide a natural check to populations of many native species. There are several types in Britain, some of which emerge from ladybird pupae instead of adult ladybirds (others deploy different but equally gruesome methods of parasitizing their hosts). This enables recorders, like me, to help scientists monitor incidences of ladybird parasitisation across the country. And it’s fun, too. I see it as a bit like having a collection of giant birthday cakes and waiting to see if a clown pops out of any of them, only much more sinister. Surprise!
One of the most common species that might emerge, clownlike, from a ladybird pupa kept in a jam jar, is the chalcid wasp Oomyzus scaposus. The female lays eggs in the larvae of unsuspecting ladybirds, and the grubs (up to 47!) complete their entire lifecycle inside the larvae, which still pupate, but don’t become adults. They emerge from the pupae as fully grown wasps within 20 days and are ready to mate in minutes.
Apparently harlequins don’t make very good hosts, so the parasitoids must evolve further before they'll make a noticeable dent in harlequin populations (c’mon chalcids). But this year I’ll collect pupae of other ladybird species too (it will make a change from ‘rescuing’ crippled bumblebees). I’ve seen several 7-spot ladybirds mating in the last few days, so I'll soon be on the lookout for pupae, which I'll pop in jam jars and then wait for the potential emergence of up to 47 chalcid wasps. Who needs telly?
Harvesting ladybird pupae is easy, but it’s important not to damage them. If they are stuck on a leaf, remove the whole leaf, and gently place it in the base of a jar (there’s no need to punch holes in the lid). Check on the pupae every day, removing and replacing the lid to refresh the air, and take a photo if anything other than a ladybird emerges. For more information and to take part, visit the Ladybird Parasite Survey.
