I recently came across a fascinating 100 years old study from Mildred Hoge (http://onlinelibrary.wiley.com/doi/10.1002/jez.1400180203/epdf).

She describes a mutation that leads to reduplication of leg or tarsal segments, in dependency of ambient temperature (look at the amazing drawings at the end of the work!). I was not able to figure out if there exists any follow-up work on this issue, maybe explaining the phenotype on a more molecular level (I'm not from the fly community). Can anyone help?