In sex-reversed cave insects, females have the penises

In this article , on April 17, Brazilian insects which represent four distinct but related species in the genus Neotrolga, are the first example of an animal with sex reversed genitalia. There have been many sex role reversal in different animals, but Neotrolgla is the only example in which the intromittment organ is also reversed says Kazunori from University of Japan. During sexual intercourse which lasts 40-70 hours, female insects insert an elaborate, penis like organ into males much reduced vagina like opening. This makes in advantages for females to mate more because of their higher nutrient count as well as sperm count. 

It will be important why only the Neotrolgla is the only to be a sex reversal role which elaborates a female penis. 

http://www.wired.com/2014/04/scientists-discover-bugs-with-sex-reversed-genitalia-doing-it-for-70-hours/http://www.wired.com/2014/04/scientists-discover-bugs-with-sex-reversed-genitalia-doing-it-for-70-hours/