Scientists accidentally release butterflies infected by parasitic wasps

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In a cautionary tale for scientists around the world, researchers introduced a new type of caterpillar to an island in Finland – inadvertently releasing three different species, two of them parasites.

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Unknown to the researchers, lurking within the caterpillars – whose movements they hoped to study as the creatures emerged in the beautiful Glanville Fritillary Butterflies – were called parasitic wasps hypomotor horticola, which feed on the caterpillar’s body contents, burst from its abdomen and spin its own cocoon around it to pupate.

But in an arguably nightmare turn of events, these parasites actually infected themselves with another species of even smaller “hyperparasitoid” wasps, called Mesocorus cf. Stigmaticus – which kill the large wasps and emerge from the bodies of the dead caterpillars 10 days later.


The third and last unexpected guest living within the caterpillar was a single-celled bacterium, known as wolbachia pipientis, which is carried by females among larger parasitic wasps and makes them more prone to infection by hyperparasitoids.

Now three decades after their accidental introduction, all four species are still alive on the island of Sotunga in the autonomous Aland archipelago.

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In a new study published in molecular Biology In the journal, scientists from the University of Helsinki analyzed genetic changes in large parasitic wasps to track their historical spread and evolution in the Baltic Sea archipelago following their accidental introduction on Sotunga.

Using 323 specimens collected in five different locations in land between 1992 and 2013, they found that parasitic wasps managed to survive on Sotunga – despite their butterfly hosts having an increasing number of dramatic population crashes, usually Due to drought, which are intensifying. as a result of climate change.

An annual survey of butterflies on Sotunga has shown that they are close to extinction. While there are Glanville fritillary butterflies that live on neighboring islands, with a maximum flight distance of about 7 km, Sotunga butterflies have been unable to reach them to breed and increase their dwindling populations.

But the new study shows that wasp parasites have managed to counter these mishaps in their host populations by flying or catching strong winds in the previously uninhabited islands in land and infecting the butterflies that live there.


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