Why do lantern flies congregate next to modern commercial buildings, specifically those with aluminum storefront system facades and black granite?

I just killed thirty in front of a high rise. The next block, a neoclassical building, had none. Crossed the street to a grocery store on the ground floor of another high rise and killed probably 40 in half the time.

Is it warmer at the base of these buildings? The two modern buildings faced each other so were in very different sun.