The whole of the reserve’s invertebrate population falls into one or more of four categories: predators, parasitoids, parasites or prey.
Predators always kill their prey. The European hornet is a predator, hunting and feeding on other invertebrate species. The adult common wasp feeds only on sugar from nectar, honeydew or fruit juices but it is, nevertheless, a ferocious predator, hunting and killing invertebrate prey to take back to the nest for its larvae.
 European hornet with prey  The jaws of a common wasp, adapted for hunting, but not eating, invertebrate prey.
Parasitoids almost always kill their prey. At least one stage of a parasitoid’s life cycle is spent in or on a prey species, eating it and, to keep it alive, saving its vital organs until last. Ichneumon wasps are parasitoids that specialise in attacking the immature stages of insects.
Few insect species escape such parasitism and and up to 50% of the caterpillars of some species of butterfly will host parasitoid larvae. Parasitoids actually play an important role as regulators of insect populations.
 A parasitoid wasp about to deposit an egg in or on a cinnabar moth caterpillar  The parasitoid larvae have left the caterpillar through its skin and pupated; the caterpillar may still be alive at this stage, its chemistry altered by the infestation so that it actually protects the pupae that are killing it.
Parasites rarely kill their victim. They live in or on another species, taking nutrition from them but not doing fatal damage.
There are many thousands of species of mite that parasitise invertebrates. The varroa mite is held responsible for the failure of many honey bee colonies but while it weakens the bee, it doesn’t kill it. What kills the bee is the viral diseases that the mites spread from hive to hive.
 Harvestman carrying parasitic mite  Honey bee covered with mites
Underpinning this list is the reserve’s plant life, the things that make the sun’s energy accessible to all the predators, parasites, parasitoids and their prey. Scientists call plants primary producers. This is where to find the prey species, the primary consumers, the browsers and munchers, the caterpillars, larvae and aphids, the herbivores of the invertebrate world, busy moving the sun’s energy one step up the food chain.
We need to look after what Sir David Attenborough calls The Whole Thing: the predators as well as their prey, the scary parasitoids, the creepy-crawlies, the squishy things, the things that make us shriek and run away. It is a network, a system, that we interfere with at our peril.
Header image: A parasitoid female field digger wasp caught by a crab spider © Line Sabroe (CC BY 2.0) wikimedia.org