Sexual stings in scorpion courtship are not just rituals

 

Sexual stings during courtship is probably one of the most fascinating behavior in scorpions. This has been documented in many species, but so far it has not been proven the the male actually penetrate the skin of the female  and if venom is injected. Some authors have characterized this behavior as "a ritual". 

Laura Olguin-Perez and co-workers have recently published a very interesting study on sexual sting in Megacormus gertschi Diaz-Najera, 1966 (Euscorpiidae). The confirm that the male penetrate the female repeatedly in the pedipalp tibia-patella intersegmental membrane just before the promenade a deux part of the courtship starts. They also confirm for the first time that the male actually injects venom into the female during the sexual stinging. Interestingly, the authors also demonstrate that the venom composition in males and females differs.

The combination of these results provide evidence that the sexual sting in scorpion courtships are more than a ritualistic behavior, but seem to have a direct role to ensure a successful courtship and mating. More research is needed to unravel the proximate effects the male venom injection has on the females and their behavior against the male.

Abstract:
The males of the Mexican species Megacormus gertschi Diaz-Najera, 1966 (Scorpiones: Euscorpiidae: Megacorminae) sting the female repeatedly in the pedipalp tibia-patella intersegmental membrane (TPIM) during the initiation of the promenade a deux. It has been suggested that the male’s venom introduced during this ‘‘sexual sting’’ behavior could generate some sedative effect and reduce the possibility of being cannibalized by the female. However, this is unsupported by evidence regarding venom transference. Here, we provide evidence of perforation of the TPIM by the male aculeus and venom transfer during sexual sting performance. We also provide the first venom characterization of this species and show that it has a sexually dimorphic composition. These results, in combination with observations that the sexual sting is displayed in successful matings with non-defensive females, lead us to consider the pre-insemination sexual stinging as a non-genitalic sexual interaction with a potential role as a courtship element.

Reference:
Olguin-Perez L, Francke OF, Carbajal-Saucedo A. Evidence of piercing and sexual differences in venom composition in a sexual stinging scorpion (Scorpiones: Euscorpiidae). J Arachnol. 2021;49:98-107. [Open Access]

Thanks to Oscar Francke for sending me their article!