Blood sucking bed bugs beat bug sprays, according to reports in ScienceDaily, BBC 13 April 2016 and PLoS doi.org/10.1371/journal.pone.0153302. For many decades bed bugs were kept under control with chemical sprays, but over the last two decades the bugs have been making a comeback.
Like all insects, bed bugs have a hard outer layer named the cuticle. Scientists at Sydney University investigated the thickness of bed bug cuticles, because, as they noted in their report, “Thickening of the integument (outer layer) as a mechanism of resistance to insecticides is a well-recognised phenomenon in the insect world”. The researchers tested common bed bugs (Cimex lectularius) for how long they could survive exposure to a pyrethroid insecticide. They then used a scanning electron microscope to measure the thickness of the cuticle in the bugs.
They found: “Mean cuticle thickness was positively correlated to time-to-knockdown, with significant differences observed between bugs knocked-down at 2 hours, 4 hours, and those still unaffected at 24 hours”. The most resistant bugs had cuticles that were 16% thicker than the least resistant bugs. This research fits with previous research that showed pyrethroid-resistant bed bugs had overexpression of cuticle depositing proteins.
The researchers commented in their report: “Insecticide resistance is a genetic change in response to selection by toxicants that impairs control in the field and is considered to be a natural evolutionary response to human-induced environmental stress”
Editorial Comment: Did you spot this one? The researchers’ comment has the conclusion backwards. The genetic changes referred to did not happen in response to selection. They never do, and indeed cannot. Natural or artificial selection can only choose between individuals who already possess the appropriate genes.
Furthermore, the genetic changes referred to by the researchers are not evolution. They are merely variations in already existing genes that control cuticle thickness. Those bugs that are already producing extra cuticle depositing proteins due to more active genes are the ones which survived the onslaught of insecticides, i.e. were selected and lived to pass on genes that made the extra proteins, so that eventually the thick skinned bugs dominated the population.
This is a good example of survival of the fittest, (or in this case, survival of the thickest), but has nothing to do with Darwinian or Dawkinsian Origin of Species since the bugs themselves are still the same species. Again the only thing evolving here is researchers’ choice to call all change evolution, when it actually isn’t. It used to be called dishonesty. (Ref. insects, resistance, artificial selection)
Evidence News, vol. 16, No. 7
27 April 2016
Creation Research Australia