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Creation 34(4):56, October 2012

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Kamikaze caterpillars


Illustrated by Caleb Salisburykamikaze

When under attack by leaf-munching insects, many plants start manufacturing special substances which act as chemical signals to attract other species that prey on the leaf-eaters. The advantages to the plant’s ability to survive are obvious, so evolutionists will of course point to natural selection as solely responsible for the phenomenon.

Researchers were puzzled, however, to discover an unusual aspect to the story in the case of tobacco plants attacked by moth caterpillars.1 It normally takes a few hours at least for such signal chemicals to be produced. Yet the caterpillar’s enemies, called ‘big-eyed bugs’,2 came almost immediately, sensing the chemicals normally released straight away from any leaf damage. These chemicals are called green leafy volatiles (GLVs). They are released from the leaf irrespective of what is causing the damage, i.e. whether by a knife, or a caterpillar’s bite. But the big-eyed bugs only came when the GLV release was caused by caterpillars. So how could they tell the difference?

Researchers found that it was not the plant, but the caterpillars themselves that rang the dinner bell for the bugs.

The GLVs come in two varieties or ‘isomers’, Z and E.3 Experiments showed it was the Z/E ratio that enabled the bugs to tell the difference between ‘normal’ leaf damage and a caterpillar bite. So what changed this ratio to alert the bugs? Researchers found that it was not the plant, but the caterpillars themselves that rang the dinner bell for the bugs. The ratio is changed by caterpillar saliva, which converts much of the Z-GLVs to E-GLVs.

This “weird and novel twist” is seen as a conundrum, because natural selection4 would be expected to act against something which makes an organism less fit to survive.

First posted on homepage: 30 December 2013
Re-posted on homepage: 2 February 2022

References and notes

  1. Fields, H., Caterpillars sign their own death warrants, www.sciencemag.org, 26 August 2010. Return to text.
  2. Geocoris spp [plural species]. Return to text.
  3. Note for chemistry buffs: Z means that the atoms with the highest atomic number are on the same side of a double bond, from German zusammen = together. E means they are on the opposite side, from entgegen = opposite. Return to text.
  4. A factual, though ultimately non-creative, process—see creation.com/muddy. Return to text.

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