I have read speculation that the crooks or kinks in the male Meloe's antennae are for the purpose of grabbing or hanging onto the female during mating. I observed something different.
Having securely mounted the female, the male uses his antennal crooks to pull the female's antennae toward each other in front of her head. After fondling her antennae with his in this way for a minute or less, he then scoots back on the female into copulation position. Although I have yet to observe actual copulation, I deduce that this antennal foreplay has the effect of making the female receptive to penetration and keeps her still while the usually smaller male assumes a more precarious perch for the sex act. I suspect that the stimulus is not just tactile, but has a chemical component, transmitted from the enlarged knobby segments that comprise the male's antennal crook. Here's a closeup:
Oh yes, the red background? Watermelon. These beetles munch leaves like a leaf beetle, but they are extremely fond of watermelon, just like stag beetles or nectar-feeding longhorns.