This large treehopper is found exclusively on black locust trees, so I understand. That is certainly where I found this impressively big one. According to Bug Guide, the female is about 14mm including the 'horn'. The male, which I've yet to see, has a strikingly vivid large yellow patch on either side. Bug Guide also notes that a single tree may have up to 500 individuals, so I definitely want to go back and check out the tree I found this one on! And, according to Bug Guide, the host tree suffers minimal to no damage from having these insects around.