by Trish Wells
Crop pests eat our food. Natural enemies are species which kill pests and include predators, parasitoids and pathogens. Natural enemies are good. Having lots of different natural enemies working in the same place, having a big team, is seen as a good thing because as things change, for example over the season or under different land management practices, it is more likely that one member of the team will be able to kill the pests. BUT! Some of the team members don’t care what they eat; they eat pests and team mates alike. How will this affect the pest populations?
There is a relatively large field within biological control research looking at this. Questions that people are working on include: How many natural enemy species do we need to maintain the levels of pest suppression we currently enjoy? Do we really need them all? If we add a particularly hungry predator will that be good because it eats more pests or will it be bad because it eats more natural enemies which may reduce the stability of pest suppression?
The ladybird (lady beetle) called the Harlequin or the multicoloured asian ladybeetle (Harmonia axyridis Pallas) is one such troublesome hungry predator. In addition, it’s a foriegn species! So everything it does in its new habitats is unusual; can the new ecosystems cope with this? This is the subject of my thesis, it took me months to think of a way to marry these two ideas, I bored people to tears when i came up with the (in retrospect obvious) solution. Anyway, below is a harrowingly beautiful clip featuring natural enemy death by the Harlequin ladybird. I helped a photographer make it.