Speciation without changes in genital shape
Published in Zool. Anz., 2005; http://dx.doi.org/10.1016/j.jcz.2004.12.001, PDF
These are the genital palps of two pholcid spider specimens that are assigned to different species based on extreme size differences and colour pattern differences. Intriguingly, the shapes of the genitalia are essentially identical. We argue that such cryptic species may be more common than currently assumed, but if marked morphological (non-genital) differences are missing, traditional taxonomic methodology is biased against discovering them.
  Photo: B. A. Huber