A typical Tipula sp. (yeah, I know, typical in that it only has four legs left).
Something new to add to the list of crane fly (Diptera: Tipulidae s.l.) stories: apparently some male crane flies are quite the Romeos with their female counterparts. In a paper that I was recently made aware of (Eberhard & Gelhaus, 2009) the authors documented a male crane fly stridulating its genitalia during copulation. The Don Juan species is a yet-to-be determined species of Tipula subgenus Bellardina from Costa Rica. A male and female were found mating and consequently video recorded. From the frames they could see the male holding the female and vibrating her genitalia using his genitalia. More precisely, he held her with the apical lobes of his ninth sternite (in a “tube” formed by them) and rasped a file on the tube with a scraper process on the outer gonostylus (part of the claspers) (see Figure 1).
The stridulation pattern can be seen in Figure 2. The whole process lasted about 10 minutes, with many small vibrations lasting a few seconds, then a long vibration period of about 20 seconds, then more small periods.
The reason for this behavior is thought to be purely to stimulate the female:
“It seems reasonable to conclude that the function of this behavior and of these structures is to stimulate the female, because stridulation behavior is ill-designed for any of the alternative functions that have been mentioned previously for genital movements, such as sensing the female, removing sperm, forcing open female passages, or penetrating more deeply.”
The authors mention that this is interesting in that it means the evolution of different genitalia in male crane flies may be following patterns other than the usually held “lock and key” or antagonistic hypotheses mentioned in the paper.
While we know that crane flies are biologically and taxonomically diverse, even this came as a surprise to me. However, it appears some members of Lepidoptera (namely Sphingidae and Pyralidae) have also evolved stridulating male genitalia. However, in moths, the males use the sound produced to call females, while in crane flies it appears to be used for vibration. Win for crane fly females!**
**And here is where I leave you with your imaginations and innuendos.