Editing Peppered moth evolution (section)

=== Phenotypic induction ===

In 1920, [[John William Heslop-Harrison]] rejected Tutt's differential bird predation hypothesis, on the basis that he did not believe that birds ate moths. Instead he proposed that pollutants could cause changes to the soma and [[germ plasm]] of the organism.<ref>{{cite journal |last=Heslop<!--sic, no hyphen--> Harrison |first=J. W. |author-link=John William Heslop-Harrison |title=Genetical studies in the moths of the geometrid genus Oporabia (Oporinia) with a special consideration of melanism in the lepidoptera |journal=[[Journal of Genetics]] |volume=9 |issue=3 |year=1920 |pages=195–280 |doi=10.1007/BF02983273 |s2cid=38996034 |url=https://www.ias.ac.in/article/fulltext/jgen/009/03/0195-0280|url-access=subscription }}</ref><!--The Royal Society describes the paper as "masterly". https://royalsocietypublishing.org/doi/pdf/10.1098/rsbm.1968.0011 --> In 1925, K. Hasebroek made an early attempt to prove this hypothesis, exposing pupae to pollutant gases, namely [[hydrogen sulfide]] (H<sub>2</sub>S), [[ammonia]] (NH<sub>3</sub>), and [[pyridine|"pyredin"]]. He used eight species in his studies, four of which were species of butterfly that did not exhibit melanism.<ref>{{cite journal |last=Hasebroek |first=K. |year=1925 |title=Die prinzipielle Loesung des Problems des Grossstadt- und Industriemelanismus der Schmetterlinge |language=de |trans-title=The principal solution of problems of city- and industrial-melanism of butterflies<!--and moths--> |journal=Internationale entomologische Zeitschrift |volume=19}}</ref> 

In 1926 and 1928, Heslop-Harrison suggested that the increase of melanic moths in industrialised regions was due to "[[mutationism|mutation pressure]]", not to selection by predators which he regarded as negligible. Salts of [[lead]] and [[manganese]] were present in the airborne pollutant particles, and he suggested that these caused the mutation of genes for melanin production but of no others. He used ''Selenia bilunaria'' and ''Tephrosia bistortata'' as material. The larvae were fed with leaves that had incorporated these salts: melanics subsequently appeared.<ref name="Heslop-Harrison Garrett 1926">{{cite journal |last1=Heslop-Harrison |first1=J. W. |author-link=John William Heslop-Harrison |last2=Garrett |first2=F. C. |title=The induction of melanism in the lepidoptera and its subsequent inheritance |journal=Proceedings of the Royal Society of London. Series B |issn=0950-1193 |volume=99 |issue=696 |year=1926 |pages=241–263 |doi=10.1098/rspb.1926.0012 |doi-access=free |s2cid=84987348 |url=https://royalsocietypublishing.org/doi/epdf/10.1098/rspb.1926.0012}}</ref><ref>{{cite journal |last=Heslop-Harrison |first=J. W. |author-link=John William Heslop-Harrison |title=A further induction of melanism in the lepidopterous insect, Selenia bilunaria Esp., and its inheritance |journal=[[Proceedings of the Royal Society of London. Series B]] |year=1928 |volume=102 |issue=718 |pages=338–347 |doi=10.1098/rspb.1928.0009 |doi-access=free}}</ref> A similar experiment in 1932 by McKenney Hughes failed to replicate these results; the statistician and geneticist [[Ronald Fisher]] showed that Heslop-Harrison's controls were inadequate, and that Hughes's findings made the 6% mutation rate required by Heslop-Harrison "improbable".<ref name="Fisher 1933">{{cite journal |last=Fisher |first=R. A. |author-link=R. A. Fisher |year=1933 |title=On the Evidence Against the Chemical Induction of Melanism in Lepidoptera |journal=[[Proceedings of the Royal Society B]] |volume=112 |issue=778 |pages=407–416 |bibcode=1933RSPSB.112..407F |doi=10.1098/rspb.1933.0018 |doi-access=free |hdl=2440/15114 |hdl-access=free}}</ref>