Wasp beetle. Photo by Sue Taylor

Black and yellow stripes don't always mean a wasp or even a sting as Sue Taylor, BBOWT volunteer recorder, explains.

We learn as small children that things that fly and are striped yellow and black are to be avoided as they sting! As we get older we learn this is not always true, but we are still wary.

Common wasp

A common wasp, Vespula vulgaris. Brilliant at pest control and pollination, and the only insect illustrated in this blog that can sting. Photo by Sue Taylor

We are not the only ones who can read these warning signs, birds, mammals, and insect predators all recognise that if something is striped black and yellow* it is to be avoided as it may sting or be poisonous to eat.

But why? How has this come about? 

Obviously being able to defend yourself is an advantage, but if the predator only realises you can sting or are toxic after you have been attacked and damaged then it’s not much use.

Six-belted clearwing moth

The six-belted clearwing moth, Bembecia ichneumoniformis, which lives off bird's-foot-trefoil. Photo by Sue Taylor

You must advertise that you can defend yourself before you are attacked, and the clearer and brighter the markings the better, so yellow and black is perfect. 

Common wasps with their potent sting are brightly banded with yellow and black, as are cinnabar caterpillars which are toxic, the warning colours work very well for both of them.

Cinnabar moth caterpillar

The yellow and black stripes on a cinnabar moth caterpillar indicate that they are toxic if eaten. Photo by Sue Taylor

But now things get more complicated. It costs the insect a lot of energy to make toxins or to equip itself to sting. Instead, many insects take the cheaper option. They have yellow and black markings, but they are completely harmless, protected by deceit.

The most successful mimics are those that most closely resemble the insect they are copying; some are very good indeed. Some copy not just the way an insect looks but also how it flies and the way it holds its wings. 

Hornet-mimic hoverflies

Hornet-mimic hoverflies, Volucella inanis, feeding on nectar. whose young are raised in hornet and wasp nests. Photo by Sue Taylor

The hornet hoverfly (Volucella zonaria) is so good it fools even the hornets, entering their nest to lay its eggs. The larvae then live in the nest protected by their predatory hosts as they scavenge debris.

Other species are poor mimics and it’s not always clear which species they are mimicking. It is even possible these are copying a species that no longer lives in the UK. Entomologists don’t regularly nibble insects(!) so some may not be mimics at all but are themselves poisonous or distasteful. As always, there is more research to be done.

Sawfly

Tenthredo thompsonii, a sawfly, related to wasps, bees and ants it eats other insects but has no sting. Photo by Sue Taylor

So, keep your eyes out for striped invertebrates. You will be surprised how many there are and the variety in their form and lifestyle.

Even if an insect can sting (and most cannot) they won’t sting you unless they are threatened by you. Keep calm, move slowly, avoid going near their nests or getting very close and even wasps and hornets will ignore you.

As for me, no way I will ignore these fascinating creatures that play such an important part in the web of life that keeps us all alive.

Sue Taylor
(Volunteer recorder for BBOWT, focusing on entomology)

*Orange/red and black are other warning combinations and here too there are both toxic insects and their mimics. It is not just insects that use these colours, fish, amphibians and reptiles too.

Wasp spider

The wasp spider, Argiope bruennichi, a relatively recent arrival to the UK that lives in grassland. Photo by Sue Taylor

 

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