Wasps. What do you think of them? Chances are you hear wasp and you think of a swarm of yellowjackets trying to ruin your summer. But actually, only a minority of hymenopteran species are stinging wasps. Many more are inoffensive parasitic wasps, which play an important ecological role.

So what is a parasitic wasp? There are many different families of parasitic wasps within the hymenopterans. They vary in size and habit, but all share one aspect of biology: parasitism. Typically, a mated female wasp will seek out an insect host and use her ovipositor to lay eggs on or inside the host body, where they will develop, hatch, and consume the host, which invariably dies. The larvae then pupate, and emerge as adults.

Parasitic wasp species can favour one particular host, or several, and host species include caterpillars, true bugs, beetles, and even spiders. In fact, it is possible that there is a parasitic wasp for every insect species on the planet. Because of their broad host base, it is thought that there could be more than a million species of parasitic wasps worldwide, more than any other insect order, including the current champion, beetles. One reason more species are not described is because unlike beetles, which were popular with historic collectors, most parasitic wasps are small and difficult to identify. This has led to myths, such as that they are one of the few creatures which decrease in diversity towards the tropics. In fact, it is likely they are highly diverse all over the planet.

They have been used purposely for biological control in agriculture more than a century. Worldwide, biological control has an estimated value of 400 billion dollars per year, of which parasitic wasps are responsible for a large proportion. Along with the economic benefits, they can also reduce the need for artificial pesticides which benefits the wider invertebrate community providing other ecosystems services, such as pollination.

Talking of pollination, although wasp larvae are carnivorous, most adult wasps feed on nectar. They have been found in half of the research datasets on pollination, they probably form a spectrum of specialist to generalist nectar feeders, making them equally important pollinators to the better known bees. Despite this, studies on ecosystems services performed by bees greatly outnumber those done on wasps. One study found 886 research papers on bees, compared to only 372 for parasitic wasps, even though the wasps have many times more species.

We have known about their importance for over a century, but even after a recent surge in interest, we know almost nothing about parasitic wasps. All we really know, is that we don’t know. Why is this? Well, one important reason is that they are small, difficult to sample, and require great expertise to distinguish. This makes them less popular with scientists.

As well as being unpopular with scientists, they are also unpopular with the public. Being small and, lets be honest, a little bit gross, parasitic wasps are unlikely to capture the imagination of the public in the way that bees have in recent years. Altogether, this means they do not attract much funding or conservation interest. Sadly, their greatest claim to public fame is a very negative quote from Darwin

So why is this a problem? Due to their high trophic level, parasitic wasps could be regarded as a keystone species, being vital in keeping a balance between phytophagous insects and plants. Because they breed much faster than vertebrates, they are more effective at matching their prey population trends. But they are sensitive to pesticides and habitat change, and because many species exist at naturally low densities, they are inherently vulnerable to extinction.

Without their predators, host species could spiral out of control, damaging biodiversity. Lack of research means we risk ignoring great benefits of these species. Without greater scientific attention and public appreciation, we are at risk of losing species, and their potential benefits, before we even know they exist.