The 2015 Nunhead Cemetery Open Day Bug Hunt has just been and gone and, as ever, one of my main tactics to enthuse children is to emphasize the grim, gory and gruesome nature of insect biology. The more disgustingly yucky the better. Dung flies are always good — they eat what? I was bitten by 20 centipedes (venomous front legs) and half-a-dozen spiders (“can you see how her fangs are stuck in my skin”). We had predatory ground beetles ready to rip apart some unfortunately prey, a hoverfly larva ready to suck an aphid’s innards out, and a lesser stag beetle grub that defaecated right on cue. But it was the parasitic wasp pupa under the ladybird that really caused a stir.
I was quite excited about this one. The idea of one animal living inside another, and eating it alive from the inside, is definitely the stuff of nightmares. No prizes for guessing where Ridley Scott got the idea for Alien.
We’d already had a couple of parasitoid wasps brought to the bug hunt stall, one with long thin ovipositor, prefect for penetrating deep into the succulent flesh of a caterpillar to lay its eggs. My description got some grimaces, but any disgust was mild, and tinged (as I had planned) with a certain amount of wonder at nature’s inventiveness. No so for Dinocampus coccinellinae, the ladybird killer.
For one thing the ladybird was not dead. It had not been allowed to die. Instead, as the maggot gnawing at its internal organs had grown to maturity, its host had continued to move about and feed, constantly supplying the hungry inner passenger with fresh food. Eventually the parasitic grub had burrowed out through the beetle’s belly to spin a cocoon in which to pupate, but still the live ladybird was in its thrall, gripping involuntarily to the leaf as a protective dome.
Hypothetical caterpillars might be one thing, but here was a helpful ‘friendly’ creature from the garden, the lead character in many a children’s book, a fashionably familiar design on back-packs, clothes, bedding, jewellery, drinking bottles, kitchen timers, hair accessories and novelty chocolates. And here it was, being tormented before our very eyes.
It was at this point that someone asked if this was one of the ‘bad’ ladybirds. Since it was first found in Essex in 2004, the harlequin ladybird, Harmonia axyridis, has been a popular tabloid focus for biological woe, with all manner of garbled non-science about its tendency to out-compete native ladybird species, and even eat them, along with lots of other ‘good’ insects like lacewing and hoverfly larvae. I suspect he was after an answer something along the lines of: “Yes, this is one of those evil foreign bugs, good thing it’s going to die, you should squish any you come across too.” I don’t think he was very impressed by my short lecture on how the concept of ‘good’ or ‘bad’ animals is nonsense to a biologist, and just the artificial construct of an ill-informed sentimental society which has lost touch with nature in all its struggle for survival — disease, decay and death.
It was at this point I realized I might be losing my audience. Perhaps I was being rather too objectively rational, and just a tad overenthusiastic about the detailed mechanics of ladybird parasitism.
Ah well, I made a slight recovery by going on to explain how the harlequin had so explosively invaded Britain, and how this common ladybird parasitoid had only recently started to increase its attacks on the alien beetle, as it became evolutionarily more familiar with the harlequin’s tree- and shrub-dwelling habits, rather than the herbage-inhabiting behaviour of the 7-spot. Anyway, the captor was suitably impressed that I wanted to keep his find, to photograph and rear the parasitoid through.
Secretly, though, I think we need to try and raise the popular understanding of some of the more awkward biological concepts — murder, incest, slavery, gender inequality, caste systems, cannibalism, and being eaten alive from the inside. I realize this is something of a challenge.