Alien

This year Salta has been unusually wet and we still have warm weather and rather heavy rains in April. This has created a true green revolution accompanied by an insect explosion. The moths are still coming in numbers to our outside lights and midgets and mosquitoes are still around.

We found a cicada that had been attracted to the verandah lights. It was rather quiet and, unusually, stayed after daybreak. I collected it without much difficulty to have a look at it as there was clearly something wrong. While having a look, my wife noted pinkish silky filaments where its abdomen should have been! In addition, it was opening its wings from time to time but not making any effort to fly.

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Dorsal view of the cicada.

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The parasitoid larva can be seen at the joint between the thorax and the abdomen.

It was during one of these wing movements that she also noted a protuberance on its dorsal area that, after some careful inspection became a small pink worm-like creature apparently lodged in it. It was about 3 mm long and somehow it reminded me of a small warble fly larva.

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The pink parasitoid seen from above with a size reference.

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A close-up of the parasitoid larva.

Further inspection revealed another couple of worms also lodged on the cicada’s flesh. The larvae were still alive as they moved when I touched them!

We decided to keep the “sick” cicada under observation. As expected it died the following day but the larvae were still there so we left it undisturbed.

It is now about one month after the find. One of the larvae that detached soon after the death of its host has apparently built a small cocoon attached to the glass jar but the other two that stayed on the dead cicada turned grey and are apparently dead.

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What I believe hatched from the cicada and made a cocoon in the glass jar.

I am afraid that the outcome of the cocoon will probably have to wait until our next visit, hopefully in 2019. In the meantime I can only speculate that, as it happens with caterpillars and other arthropods, the cicada was the victim of some parasitoids that have somehow colonized it. It is likely, as we other situations like this, that the larvae had eaten the cicada slowly until the damage created caused it to perish but not before the parasitoids, or at least some, were ready to leave the body and develop.

I will venture that these are larvae of a parasitoid wasp but I cannot be sure until the small cocoon hatches, if it ever does. However, having seen such an interesting interaction, I will watch for another cicada showing similar signs and follow it up.

 

Postcript: In the internet I learnt that some flies are important parasitoids of cicadas and that they locate them through their sound. It is also possible that the silky, pinkish filaments could be a fungal infection that follows the parasitoid’s damage of the host.

 

 

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