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Parasitic wasps morph fellow insects into zombies

The behavior of the parasitic creature in the science fiction film “Alien” is similar to that of a real-life parasitic wasp, said George Hamilton, chair of the Department of Entomology.

Certain species of parasitic wasps reproduce by injecting behavior-altering chemicals into a host insect.

A parasitic wasp takes over the neurosystem of the host and lays an egg inside the host, Hamilton said.

“The larvae of the wasp then eats the internal contents of the insect and then emerges from there,” Hamilton said.

After the larvae has been laid, Hamilton said the host insect will act in ways different from its normal behavior.

Hamilton gave other examples of behavior-altering organisms, such as fungi that can take over the brains of ants. The fungi will cause the ant to climb to the top of foliage and stay there, until the fungi bursts out of the ant’s head and releases its spores.

Parasitic wasps can actually be used in beneficial ways, such as pest control. In Hamilton's research, parasitic wasps were used to control Colorado potato beetles and European corn borers, both of which are major crop pests.

Currently, the biggest pest in New Jersey is the emerald ash borer, Hamilton said. It was introduced to Michigan about 10 years ago and has been advancing toward the East Coast.

The ash borer is a beetle that attacks ash trees. Since ash trees are forest plants, spraying chemicals is not an effective method, Hamilton said. In response, the Department of Agriculture is releasing wasps imported from Asia, the borers’ native land, to deal with these ash borers.

These wasps pose no threat to humans, Hamilton said. Before the wasps are released, they are subjected to an extended period of quarantine, during which certain species of insects are “suggested” to the wasps.

After the quarantine, the wasps are fairly specific in selecting targets. The wasps can even be so specific as to only target one species, such as the ash borer.

These wasps are also not capable of hurting humans. Their equivalent of a stinger is for laying eggs and is not strong enough to puncture human skin.

This method of using parasitic insects has been used to fight pests on a large scale.

One example is the effort to control the gypsy moth, a pest that damages hardwood trees. Over the last hundred years, around a hundred different organisms have been released to control the gypsy moth.

The great majority of these organisms are insects, including parasitic wasps. These insects eat the larvae of the gypsy moth.

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