This pattern appears influenced by body temperature, like the pattern seen in Siamese cats, region of the body that are cooler have darker pigmentation. It is notable that this is a rather detailed pattern for such a small animal as K. picta is really quite small. Myotis hermani is also similarly patterned, apparently. And so is Lasiurus borealis, the red bat, whose small face looks like a bat version of Pikachu.
A few months ago I speculated about the possiblity of "seabats" here. I just learned that such creatures do exist. From a post in the series on bats Naish writes:
The foot claws of some species - most notably the Fishing bat Myotis vivesi - are extremely impressive or totally ridiculous, depending on your opinion. In case you didn't know, this bat (unique to the coasts of the Gulf of California) fishes at sea - a pretty incredible bit of behaviour that has led some biologists to describe it as an honorary marine mammal.Recently I also came across an old photo of a bat about to eat a frog. Were I to title it, I'd call it "death by winged teeth":